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)

#
import sys
import math
import numpy as np
import itertools


# ひとつ入力
n = int(input())
# 空白区切りの数列をリストに代入
t = [int(i) for i in input().split()] 

t.sort()

for i in range(1,n):
    if t[i]==t[i-1]:
        print("NO")
        exit()
print("YES")