import sys

N=int(input())
A=list(map(int,input().split()))
A.sort()
for i in range(N-1):
  if(A[i]==A[i+1]):
    print("NO")
    sys.exit()
print("YES") import sys sys 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 A.sort() A.sort A sort for i in range(N-1):
  if(A[i]==A[i+1]):
    print("NO")
    sys.exit() i range(N-1) range N-1 N 1 if(A[i]==A[i+1]):
    print("NO")
    sys.exit() A[i]==A[i+1] A[i] A i A[i+1] A i+1 i 1 print("NO") print "NO" sys.exit() sys.exit sys exit print("YES") print "YES" N=int(input()) int(input()) N A=list(map(int,input().split())) list(map(int,input().split())) A
import sys

N=int(input())
A=list(map(int,input().split()))
A.sort()
for i in range(N-1):
  if(A[i]==A[i+1]):
    print("NO")
    sys.exit()
print("YES")