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: Accepted)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int compare_int(const void *a, const void *b)
{
    return *(int*)a - *(int*)b;
}

int main(void)
{
    unsigned int N;
    unsigned int A[200000];
    unsigned int i, counter = 0;

    scanf("%d", &N);
    for (i = 0; i < N; i++)
    {
        scanf("%d", &A[i]);
        counter++;
    }
    qsort(A, counter, sizeof(int), compare_int);
    for (i = 0; i < N; i++)
    {
        if (A[i + 1] != '\0' && A[i] == A[i + 1])
        {
            printf("NO");
            return (0);
        }
    }
    printf("YES");
    return (0);
}