diff --git a/.idea/misc.xml b/.idea/misc.xml
index a165cb3..dc565b0 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="ProjectRootManager" version="2" default="false" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" default="false" project-jdk-name="10" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>
\ No newline at end of file
diff --git a/src/flashcards/Main.java b/src/flashcards/Main.java
index d1b036c..18adb6a 100644
--- a/src/flashcards/Main.java
+++ b/src/flashcards/Main.java
@@ -1,7 +1,245 @@
 package flashcards;
 
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Scanner;
+
 public class Main {
-    public static void main(String[] args) {
-        System.out.print("Hello world!");
+
+  private static final String IMPORT_OPT = "-import";
+  private static final String EXPORT_OPT = "-export";
+
+  private static Map<String, String> cardToDefinition = new LinkedHashMap<>();
+  private static Map<String, String> definitionToCard = new LinkedHashMap<>();
+  private static List<String> logs = new ArrayList<>();
+  private static Map<String, Integer> stats = new HashMap<>();
+
+  private static Path importPath = null;
+  private static Path exportPath = null;
+
+  public static void main(String[] args) {
+    if (args.length > 0) {
+      String[][] optPairs = new String[args.length / 2][2];
+      int i = 0, j = 0;
+      while (i < args.length - 1) {
+        optPairs[j][0] = args[i];
+        optPairs[j][1] = args[i + 1];
+        i += 2;
+        j++;
+      }
+      assignOpts(optPairs);
+    }
+    if (importPath != null) {
+      importCard(importPath);
+    }
+    try (Scanner scanner = new Scanner(System.in)) {
+      while (true) {
+        System.out.println(
+            "Input the action (add, remove, import, export, ask, exit, log, hardest card, reset stats):");
+
+        String action = scanner.nextLine();
+
+        logs.add(action);
+
+        switch (action) {
+          case "add":
+            addCard(scanner);
+            break;
+          case "remove":
+            removeCard(scanner);
+            break;
+          case "import":
+            importCard(scanner);
+            break;
+          case "export":
+            exportCard(scanner);
+            break;
+          case "ask":
+            askCard(scanner);
+            break;
+          case "exit":
+            if (exportPath != null) {
+              exportCard(exportPath);
+            }
+            System.out.println("Bye bye!");
+            return;
+          case "log":
+            log(scanner);
+            break;
+          case "hardest card":
+            hardestCard();
+            break;
+          case "reset stats":
+            resetStats();
+            break;
+        }
+      }
+    }
+  }
+
+  private static void assignOpts(String[][] optPairs) {
+    for (String[] opt : optPairs) {
+      switch (opt[0]) {
+        case IMPORT_OPT:
+          importPath = Paths.get(opt[1]);
+          break;
+        case EXPORT_OPT:
+          exportPath = Paths.get(opt[1]);
+          break;
+      }
+    }
+  }
+
+  private static void resetStats() {
+    stats.clear();
+    System.out.printf("\n");
+  }
+
+  private static void hardestCard() {
+    Iterator<Entry<String, Integer>> iterator = stats.entrySet().iterator();
+    Entry<String, Integer> maxErrors = iterator.hasNext() ? iterator.next() : null;
+    if (maxErrors == null) {
+      System.out.printf("No stats\n\n");
+      return;
     }
+    while (iterator.hasNext()) {
+      Entry<String, Integer> cur = iterator.next();
+      if (cur.getValue() > maxErrors.getValue()) {
+        maxErrors = cur;
+      }
+    }
+    System.out.printf("The hardest card is \"%s\". You have %d errors answering it.\n\n",
+        maxErrors.getKey(), maxErrors.getValue());
+  }
+
+  private static void log(Scanner scanner) {
+    System.out.println("File name:");
+    String fileName = scanner.nextLine();
+    logs.add(fileName);
+    try (BufferedWriter writer = Files.newBufferedWriter(Paths.get(fileName));
+        PrintWriter print = new PrintWriter(writer)) {
+      for (String entry : logs) {
+        print.printf("%s\n", entry);
+      }
+      logs.clear();
+    } catch (IOException e) {
+      System.out.printf("The log has not been saved.\n\n");
+      return;
+    }
+    System.out.printf("The log has been saved..\n\n");
+  }
+
+  private static void askCard(Scanner scanner) {
+    System.out.println("How many times to ask?");
+    String num = scanner.nextLine();
+    logs.add(num);
+    int n = Integer.parseInt(num);
+    for (String card : cardToDefinition.keySet()) {
+      if (n <= 0) {
+        break;
+      }
+      System.out.printf("Print the definition of \"%s\":\n", card);
+      String guess = scanner.nextLine();
+      logs.add(guess);
+      if (definitionToCard.containsKey(guess) && cardToDefinition.get(card).equals(guess)) {
+        System.out.printf("Correct answer.\n");
+      } else if (definitionToCard.containsKey(guess)) {
+        System.out.printf(
+            "Wrong answer (the correct one is \"%s\", you've just written a definition of \"%s\" card).\n",
+            cardToDefinition.get(card), definitionToCard.get(guess));
+        stats.merge(card, 1, (x, y) -> x + y);
+      } else {
+        System.out
+            .printf("Wrong answer (the correct one is \"%s\").\n", cardToDefinition.get(card));
+        stats.merge(card, 1, (x, y) -> x + y);
+      }
+      n--;
+    }
+    System.out.printf("\n");
+  }
+
+  private static void exportCard(Scanner scanner) {
+    System.out.println("File name:");
+    String fileName = scanner.nextLine();
+    logs.add(fileName);
+    exportCard(Paths.get(fileName));
+  }
+
+  private static void exportCard(Path fileName) {
+    try (BufferedWriter writer = Files.newBufferedWriter(fileName);
+        PrintWriter print = new PrintWriter(writer)) {
+      for (Entry<String, String> entry : cardToDefinition.entrySet()) {
+        print.printf("%s\n%s\n", entry.getKey(), entry.getValue());
+      }
+    } catch (IOException e) {
+      System.out.printf("0 cards have been saved.\n\n");
+      return;
+    }
+    System.out.printf("%d cards have been saved.\n\n", cardToDefinition.size());
+  }
+
+  private static void importCard(Scanner scanner) {
+    System.out.println("File name:");
+    String fileName = scanner.nextLine();
+    logs.add(fileName);
+    importCard(Paths.get(fileName));
+  }
+
+  private static void importCard(Path fileName) {
+    int count = 0;
+    try (BufferedReader reader = Files.newBufferedReader(fileName)) {
+      String card;
+      while ((card = reader.readLine()) != null) {
+        String def = reader.readLine();
+        if (def == null) {
+          break;
+        }
+        cardToDefinition.put(card, def);
+        definitionToCard.put(def, card);
+        count++;
+      }
+    } catch (IOException e) {
+      System.out.printf("0 cards have been read.\n\n");
+      return;
+    }
+    System.out.printf("%d cards have been read.\n\n", count);
+  }
+
+  private static void removeCard(Scanner scanner) {
+    System.out.println("The card:");
+    String card = scanner.nextLine();
+    logs.add(card);
+    if (cardToDefinition.containsKey(card)) {
+      String def = cardToDefinition.get(card);
+      definitionToCard.remove(def);
+      cardToDefinition.remove(card);
+      System.out.println("The card successfully removed\n\n");
+    } else {
+      System.out.printf("Can't remove \"%s\": there is no such card.\n\n", card);
+    }
+  }
+
+  private static void addCard(Scanner scanner) {
+    System.out.println("The card:");
+    String card = scanner.nextLine();
+    logs.add(card);
+    System.out.println("The definition of the card:");
+    String definition = scanner.nextLine();
+    logs.add(definition);
+    cardToDefinition.put(card, definition);
+    definitionToCard.put(definition, card);
+    System.out.printf("The pair (\"%s\":\"%s\") is added.\n\n", card, definition);
+  }
 }
\ No newline at end of file