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 9.2.1) (judge verdict: Accepted)

#include <cmath>
#include <iostream>
#include <stack>
#include <map>
#include <set>
#include <vector>
#include <algorithm>

using namespace std;

#define rep(i, n) for (int p = i; p < n; p++)

bool option(pair<int, int>& a, pair<int, int>& b) {
    return a.second < b.second;
}

int main() {
    bool f = true;
    int n, tmp;
    map<int, int> a;
    map<int, int>::iterator it;

    cin >> n;

    rep(0, n) {
        cin >> tmp;
        a[tmp]++;
    }

    for (it = a.begin(); it != a.end(); it++) {
        if (it->second > 1) {
            f = !f;
            break;
        }
    }

    cout << ((f) ? "YES" : "NO") << endl;

    return 0;
}