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: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)

int main(){
    int n;
    cin >>n;
    int count = 0;
    vector<int> A(n);
    rep(i,n){
        cin >> A[i];
    }
    map<int,int> m;
    bool ans = true;
    for(int x :A){
        if(m.count(x)){
            ans =false;
        }else{
            m[x]=1;
        }
    }
    if(ans)
        cout<<"YES"<<endl;
    else
        cout<<"NO"<<endl;
}