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 <inttypes.h>
#include <math.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int compare(const void *a, const void *b)
{
    if (*(intmax_t *)a < *(intmax_t *)b)
        return -1;
    if (*(intmax_t *)a > *(intmax_t *)b)
        return 1;
    return 0;
}

int main(void)
{
    intmax_t N, A[200000];
    intmax_t ans = 0;

    scanf("%jd", &N);
    for (size_t i = 0; i < N; i++) {
        scanf("%jd", &A[i]);
    }

    qsort(A, N, sizeof(A[0]), compare);

    for (size_t i = 1; i < N; i++) {
        if (A[i] == A[i - 1]) {
            puts("NO");
            return 0;
        }
    }

    puts("YES");

    return 0;
}