solution code of Modular Equation problem number-5 of may long challenge codechef

 Modular Equation Problem Code: CodeChef

Solution Code

#include<bits/stdc++.h>

using namespace std;

#define int long long int

#define endl "\n"

int32_t main()

{

    ios_base::sync_with_stdio(false);

    cin.tie(0);

    int t;cin>>t;

    while(t--)

    {

        int n, m;cin>>n>>m;

        int count_of_pair = 0;

        vector<int> modular_equation(n+1, 1);

        for(int a = 2;a<=n;a++)

        {

            int x = m%a;

            count_of_pair += modular_equation[x];

            for(int b = x;b<=n;b+=a)

            {

                modular_equation[b]++;

            }

        }

        cout<<count_of_pair<<endl;

    }

    return 0;

}