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 N, A[300000], i, t;
    int num = 1;

    scanf("%d", &N);
    for(i = 1; i <= N; i++)
        scanf("%d", &A[i]);

    for(i = 1; i < N; i++) {
        for(t = i + 1; t <= N; t++)
            if (A[i] == A[t])
                num = 0;
    }

    if (num)
        printf("YES");
    else
        printf("NO");

	return 0;
}