/*
Solution Author: Pavel Glushen
Date: 29.04.2018
*/

#include <iostream>
#include <unordered_map>
#include <cmath>
using namespace std;

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int n;
    cin >> n;

    unordered_map<int, int> count;

    for (int i = 0; i < n; i++)
    {
        int t;
        cin >> t;
        
        count[t]++;
    }

    for (auto p : count)
    {
        if (p.first > 0 && p.second == p.first * p.first)
        {
            cout << "YES";
            return 0;
        }
    }

    cout << "NO";
}