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 C (GCC 5.4.1) (judge verdict: Runtime Error)

#include <stdio.h>

int main()
{
	int i, k, flag = 0;
	int N, A[20000];
	scanf("%d",&N);
	for(i = 0; i < N; i++){
		scanf("%d", &A[i]);
	}
	for(i = 0;i < N; i++){
		k = i + 1;
		while(k < N){
			if(A[i] == A[k]){
				flag = 1;
			}
			k++;
			if(flag==1) break;
		}
		if(flag==1) break;
	}
	if(flag == 1) printf("NO");
	else printf("YES");
    return 0;
}