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: Time Limit Exceeded)

#include<stdio.h>
int main()
{
    int a[200000], j,k,i,n;
	i=0;
	
	scanf("%d", &n);
	scanf("%d", &a[0]);
	k=1;
	for(i=1; i<n;i++){
		
		scanf("%d", &a[i]);
	for(j=0; j<k; j++){
		
			if(a[k]==a[j]){
				printf("NO\n");
				return 0;
			}

		}
				k++;
	}
	printf("YES");
		    return 0;
}