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)++)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define ll long long
#define pii pair<int,int> 
#define Yes cout << "Yes" << endl
#define No cout << "No" << endl
#define YES cout << "YES" << endl
#define NO cout << "NO" << endl
int inf=1000001000;
ll INF=100000000000000000;
ll MOD=1000000007;
//g++ code.cpp   ./a.out 
 
int main() {
    int n; cin >> n;
    vector<int> a(n); 
    rep(i,n) cin >> a[i];
    sort(a.begin(),a.end());
    rep(i,n){
        if(a[i+1]==a[i]) {
             NO;
             return 0;
        }     
    }
    YES;
}