Problem:
Score : 300 points

Problem Statement

Given is a sequence of integers A_1, A_2, ..., A_N.
If its elements are pairwise distinct, print YES; otherwise, print NO.

Constraints

2 ≤ N ≤ 200000

1 ≤ A_i ≤ 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 ... A_N

Output

If the elements of the sequence are pairwise distinct, print YES; otherwise, print NO.

Sample Input 1

5
2 6 1 4 5

Sample Output 1

YES

The elements are pairwise distinct.

Sample Input 2

6
4 1 3 1 6 2

Sample Output 2

NO

The second and fourth elements are identical.

Sample Input 3

2
10000000 10000000

Sample Output 3

NO

Solution in Python (3.4.3) (judge verdict: Accepted)

#At coder 2020/2/9 B

# 入力
N = int(input())
A = list(map(int, input().split())) 

if len(A)-len(set(A))==0:
    ans='YES'
else:
    ans='NO'
#ans='YES'
#for ii in range(N-1):
#    for jj in range(ii+1,N):
#        if A[ii]==A[jj]:
#            ans='NO'
#            break
#    if ans=='NO':
#        break


print(ans)