def main():
    n = int(input())
    a = tuple(map(int, input().split()))
    if n == len(set(a)):
        print('YES')
    else:
        print('NO')

if __name__ == '__main__':
    main() def main():
    n = int(input())
    a = tuple(map(int, input().split()))
    if n == len(set(a)):
        print('YES')
    else:
        print('NO') main n = int(input()) n int(input()) int input() input a = tuple(map(int, input().split())) a tuple(map(int, input().split())) tuple map(int, input().split()) map int input().split() ().split () input split if n == len(set(a)):
        print('YES')
    else:
        print('NO') n == len(set(a)) n len(set(a)) len set(a) set a print('YES') print 'YES' print('NO') print 'NO' if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    n = int(input())
    a = tuple(map(int, input().split()))
    if n == len(set(a)):
        print('YES')
    else:
        print('NO') def main():
    n = int(input())
    a = tuple(map(int, input().split()))
    if n == len(set(a)):
        print('YES')
    else:
        print('NO') main
def main():
    n = int(input())
    a = tuple(map(int, input().split()))
    if n == len(set(a)):
        print('YES')
    else:
        print('NO')

if __name__ == '__main__':
    main()
