def check(seq):
    return len(seq) != len(set(seq))

def main():
  N = int(input())
  A = list(map(int, input().split()))
  ans = check(A)
  if ans:
    print("NO")
  else:
    print("YES")
main() def check(seq):
    return len(seq) != len(set(seq)) check return len(seq) != len(set(seq)) len(seq) != len(set(seq)) len(seq) len seq len(set(seq)) len set(seq) set seq seq seq def main():
  N = int(input())
  A = list(map(int, input().split()))
  ans = check(A)
  if ans:
    print("NO")
  else:
    print("YES") main N = int(input()) N int(input()) int input() input A = list(map(int, input().split())) A list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split ans = check(A) ans check(A) check A if ans:
    print("NO")
  else:
    print("YES") ans print("NO") print "NO" print("YES") print "YES" main() main def check(seq):
    return len(seq) != len(set(seq)) def check(seq):
    return len(seq) != len(set(seq)) check def main():
  N = int(input())
  A = list(map(int, input().split()))
  ans = check(A)
  if ans:
    print("NO")
  else:
    print("YES") def main():
  N = int(input())
  A = list(map(int, input().split()))
  ans = check(A)
  if ans:
    print("NO")
  else:
    print("YES") main
def check(seq):
    return len(seq) != len(set(seq))

def main():
  N = int(input())
  A = list(map(int, input().split()))
  ans = check(A)
  if ans:
    print("NO")
  else:
    print("YES")
main()