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: Accepted)

#include <string.h>
#include <stdlib.h>
int compare_int(const void *a, const void *b)
{
    return *(int *)a - *(int *)b; //昇順になる
}
int main(void) //qsort等しないと時間かかりすぎみたいね
{
    int N;
    int a[200000];
    for (int i = 0; i < 200000; i++)
    {
        a[i] = -1;
    }
    int flag = 0;
    scanf("%d", &N);
    for (int i = 0; i < N; i++)
    {
        scanf("%d", &a[i]);
    }
    qsort(a, N, sizeof(int), compare_int);
    for (int i = 0; i < N - 1; i++)
    {
        if (a[i] == a[i + 1])
        {
            printf("NO");
            flag = 1;
            break;
        }
    }

    if (flag == 0)
    {
        printf("YES");
    }
    return 0;
}