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>

#ifdef TEST
struct test {
    int ans;
} td[] = {
    {},
};
#endif

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

void
solver(long n, long *a)
{
    long i;
    long p;

    qsort(a, n, sizeof(long), cmp);

    p = a[0];
    for(i = 1; i < n; i++) {
        if(p == a[i]) {
            printf("NO\n");
            return;
        }
        p = a[i];
    }
    printf("YES\n");
}

int
main(int argc, char *argv[])
{
    long N;
    long A[200000];
    long i;
#ifdef TEST
    int tt;
    for(tt = 0; tt < sizeof(td) / sizeof(struct test); tt++) {
        solver();
        printf("%d\n", td[tt].ans);
    }
#endif
    scanf("%ld", &N);
    for(i = 0; i < N; i++)
        scanf("%ld", A + i);
    solver(N, A);
    return 0;
}