import java.util.HashSet;
              import java.util.Scanner;
              import java.util.Set;
              
              public class DuplicateNumberChecker7078 {
              
                  public static void main(String[] args) {
                      try {
                          Set numbers = readNumbersFromUser();
                          checkForDuplicates(numbers);
                          System.out.println("No duplicate numbers found.");
                      } catch (DuplicateNumberException e) {
                          System.err.println("Error: " + e.getMessage());
                          e.printStackTrace();
                      }
                  }
              
                  public static Set readNumbersFromUser() {
                      Set numbers = new HashSet<>();
                      Scanner scanner = new Scanner(System.in);
              
                      System.out.print("Enter the number of integers: ");
                      int count = scanner.nextInt();
              
                      System.out.println("Enter the integers:");
              
                      for (int i = 0; i < count; i++) {
                          int num = scanner.nextInt();
                          numbers.add(num);
                      }
              
                      scanner.close();
                      return numbers;
                  }
              
                  public static void checkForDuplicates(Set numbers) throws DuplicateNumberException {
                      Set uniqueNumbers = new HashSet<>();
              
                      for (int number : numbers) {
                          if (!uniqueNumbers.add(number)) {
                              throw new DuplicateNumberException("Duplicate number found: " + number);
                          }
                      }
                  }
              }
              
              class DuplicateNumberException extends Exception {
                  public DuplicateNumberException(String message) {
                      super(message);
                  }
              }