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(void){
    
    int num,i,j;
    int a[1000000];
    int hantei = 0;
    
    scanf("%d",&num);
    
    for(i=0; i<num; i++){
        scanf("%d",&a[i]);
    }
    
    for(i=0; i<num; i++){
        for(j=i+1; j<num; j++){
            if(a[i]==a[j]){
                hantei = 1;
            }
        }
    }

    if(hantei == 1){
        printf("NO");
    }else if(hantei == 0){
        printf("YES");
    }
    return 0;
}