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>
#include <stdlib.h>
#include <stdbool.h>
 
int main()
{
    int i, na, j;
    int *a;
    //int b= 0;
    bool exit= false;
    
    printf("\n");
    if(scanf("%d", &na)==1)
    {
    a= calloc(na, sizeof(int));
  
        for(i=1; i<na+1; i++)
        {
            printf("\n");
            if(scanf("%d", &a[i])==1&&i==na)
            {
                for(i=1; i<na+1; i++){
                    for(j = 1; j<na-i+1; j++)
                    {
                        if(a[i]==a[i+j])
                        {
                            exit= true;
                            break;
                        }
                    }
                    if(exit==true)
                        break;
                }
                if(exit== true)
                {
                    printf("NO");
                    return(0);
                }
                printf("YES");
                return(0);
            }
        }
  
        //free(a);
    }
}