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: Time Limit Exceeded)

n = int(input())
x = [int(x) for x in input().split()]
flag = 0
for i in range(len(x)):
    for j in range(len(x)):
        if i != j:
            if x[i] == x[j]:
                print("NO")
                flag = 1
                break
    if flag == 1:
        break
else:
    print("YES")