#!/usr/bin/env python3
def main():
    N = int(input())
    print('YES' if len(set(input().split())) == N else 'NO')


if __name__ == '__main__':
    main() def main():
    N = int(input())
    print('YES' if len(set(input().split())) == N else 'NO') main N = int(input()) N int(input()) int input() input print('YES' if len(set(input().split())) == N else 'NO') print 'YES' if len(set(input().split())) == N else 'NO' len(set(input().split())) == N len(set(input().split())) len set(input().split()) set input().split() ().split () input split N 'YES' 'NO' if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    N = int(input())
    print('YES' if len(set(input().split())) == N else 'NO') def main():
    N = int(input())
    print('YES' if len(set(input().split())) == N else 'NO') main
#!/usr/bin/env python3
def main():
    N = int(input())
    print('YES' if len(set(input().split())) == N else 'NO')


if __name__ == '__main__':
    main()
