n = int(input())
import sys
an = list(map(int, sys.stdin.readline().split()))

if len(set(an))==n:
    print('YES')
    exit(0)

print('NO') n = int(input()) n int(input()) int input() input import sys sys an = list(map(int, sys.stdin.readline().split())) an list(map(int, sys.stdin.readline().split())) list map(int, sys.stdin.readline().split()) map int sys.stdin.readline().split() sys.stdin.readline().split sys.stdin.readline() sys.stdin.readline sys.stdin sys stdin readline split if len(set(an))==n:
    print('YES')
    exit(0) len(set(an))==n len(set(an)) len set(an) set an n print('YES') print 'YES' exit(0) exit 0 print('NO') print 'NO' an = list(map(int, sys.stdin.readline().split())) list(map(int, sys.stdin.readline().split())) an n = int(input()) int(input()) n
n = int(input())
import sys
an = list(map(int, sys.stdin.readline().split()))

if len(set(an))==n:
    print('YES')
    exit(0)

print('NO')