1512G - Short Task - CodeForces Solution

#include <bits/stdc++.h>
typedef long long ll;
using namespace std;

const int N = 1e7 + 2 ;
vector<ll> divisors(N+1 , 1);
vector<ll>arr(N) ;

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int tc;
    tc = 1;
    cin >> tc;
    divisors[1] = 1 ;
    for (int i = 2; i < N; i++) {
        for (int j = i; j < N; j += i) {
            divisors[j] += i * 1ll ;
        }
    }
    for(int i = 1 ;i<N; i++){
        if(divisors[i] < N && arr[divisors[i]] == 0)
            arr[divisors[i]] = i ;
    }
    while (tc--)
    {
        int c ;
        cin >> c ;
        cout<<(arr[c] ? arr[c] : -1)<<endl;
    }
}