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>
void sort(int A[], int len_A){
    int i, j, tmp;
    for (i = 0; i < len_A - 1; i++){
        for (j = 0; j < len_A - 1; j++){
            if (A[j + 1] < A[j]){
                tmp = A[j];
                A[j] = A[j + 1];
                A[j + 1] = tmp;
            }
        }
    }
}


int main(void){
    int n;
    scanf("%d", &n);
    int a[n];
    for (int i = 0; i < n; i++){
        scanf("%d", &a[i]);
    }

    /*
    int flag = 1;
    for (int i = 0; i < n; i++){
        for (int j = i + 1; j < n; j++){
            if (a[i] == a[j]){
                flag = 0;
            }
        }
    }
    */

    int flag = 1;
    sort(a, n);
    for (int i = 0; i < n - 1; i++){
        if (a[i] == a[i + 1]){
            flag = 0;
        }
    }

    if (flag){
        printf("%s\n", "YES");
    }
    else {
        printf("%s\n", "NO");
    }

    return 0;
}