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++14 (GCC 5.4.1) (judge verdict: Time Limit Exceeded)

#include <iostream>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <string>
#include <utility>

using namespace std;

int main()
{
    int n,x;
    cin >> n;
    int a[n];

    for(int i=0;i<n;i++){
        cin >> x;
        a[i] = x;
    }
    
    for(int i=0;i<n;i++){
        for(int j=i+1; j<n; j++){
            if(a[i]==a[j]){
                cout << "NO";
                return 0;
            }
        }
    }
    
    cout << "YES";
    return 0;
}
/*
    int m,n,k,cand;
    cin >> m >> n >> k;

    int a[m+1] = {0};
    a[0] = n;

    for(int i=0;i<k;i++){
        cin >> cand;
        for(int j=0; j<m+1; j++){
            if(a[j]>0){
                a[j]--;
                a[cand]++;
            }
        }
    }
    
    int maxi=0;
    for(int i=1;i<m+1;i++){
        if(a[i]>maxi) 
            maxi = a[i];
    }

    for(int i=1;i<m+1;i++){
        if(a[i]==maxi) 
            cout << i << endl;
    }


    for(int i=1;i<m+1;i++){
        cout << a[i] << endl;
    }
*/