import sys

read = sys.stdin.read
readline = sys.stdin.readline
readlines = sys.stdin.readlines
sys.setrecursionlimit(10 ** 9)
INF = 1 << 60
MOD = 1000000007


def main():
    N, *A= map(int, read().split())
    
    if len(set(A)) == N:
        print('YES')
    else:
        print('NO')
    
    return


if __name__ == '__main__':
    main() import sys sys read = sys.stdin.read read sys.stdin.read sys.stdin sys stdin read readline = sys.stdin.readline readline sys.stdin.readline sys.stdin sys stdin readline readlines = sys.stdin.readlines readlines sys.stdin.readlines sys.stdin sys stdin readlines sys.setrecursionlimit(10 ** 9) sys.setrecursionlimit sys setrecursionlimit 10 ** 9 10 9 INF = 1 << 60 INF 1 << 60 1 60 MOD = 1000000007 MOD 1000000007 def main():
    N, *A= map(int, read().split())
    
    if len(set(A)) == N:
        print('YES')
    else:
        print('NO')
    
    return main N, *A= map(int, read().split()) N map(int, read().split()) map int read().split() ().split () read split *A A if len(set(A)) == N:
        print('YES')
    else:
        print('NO')
    
     len(set(A)) == N len(set(A)) len set(A) set A N print('YES') print 'YES' print('NO') print 'NO' return if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main readlines = sys.stdin.readlines sys.stdin.readlines readlines INF = 1 << 60 1 << 60 INF read = sys.stdin.read sys.stdin.read read readline = sys.stdin.readline sys.stdin.readline readline def main():
    N, *A= map(int, read().split())
    
    if len(set(A)) == N:
        print('YES')
    else:
        print('NO')
    
    return def main():
    N, *A= map(int, read().split())
    
    if len(set(A)) == N:
        print('YES')
    else:
        print('NO')
    
    return main MOD = 1000000007 1000000007 MOD
import sys

read = sys.stdin.read
readline = sys.stdin.readline
readlines = sys.stdin.readlines
sys.setrecursionlimit(10 ** 9)
INF = 1 << 60
MOD = 1000000007


def main():
    N, *A= map(int, read().split())
    
    if len(set(A)) == N:
        print('YES')
    else:
        print('NO')
    
    return


if __name__ == '__main__':
    main()
