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 (Clang 3.8.0) (judge verdict: Time Limit Exceeded)

#include <stdio.h>
#define NUMBER 2000000
int main(void)
{
    int n;
    int a[NUMBER];
    int i,j;
    int c = 1;
    
    scanf("%d",&n);
    for (i = 0;i < n;i++){
        scanf("%d",&a[i]);
    }
    
    for (i = 0;i < n-1;i++){
        for (j = i+1;j < n;j++){
            if (a[i] == a[j]){
                c = 0;
                break;
            }
        }
    }
    
    if (c == 0){
        printf("NO\n");
    }
    else{
        printf("YES\n");
    }
    
    return 0;
}