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,x;

    scanf("%d", &num);

    int array1[num],array2[num];

    for(x = 1; x <= num; x++)
    {
        scanf("%d ", &array1[x]);
        array2[x] = array1[x];
    }

    int i,j;
    
    int count;
    int pass = 0;

    for(i = 1; i <= num; i++)
    {
        count = 0;
        
        for(j = 1; j <= num; j++)
        {
            if(array1[i] == array2[j])
                count++;
        }
        if(count >= 2)
            pass++;
    }

    if(pass >= 2)
        printf("NO\n");
    else
        printf("YES\n");

    return 0;
}