Configuration System

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

int main(){
    int n, s0, k, b, m, a;
    cin >> n >> s0 >> k >> b >> m >> a;

    vector<int> s(n, 0);
    s[0] = s0;
    for(int i=1; i<n; i++){
        s[i] = ( (k * s[i-1] + b) % m ) + 1 + s[i-1];
        //cout << s[i] << " ";
    }
    //cout << endl << endl;

    //obviously s will be in sorted order....
    int i=0, j=n-1;
    int answer = 0;

    while(i<=j){
        int pro = s[i] * s[j];
        if(pro <= a){
            //it means that all the pairs with i = i and j <=j will be counted
            answer += 2 * (j-i);    answer+= 1;
            i++;
        }
        else{
            j--;
        }
    }
    cout << answer << endl;
    return 0;
}

/*
    Area not more than a (of ceiling)

    First task is to generate s...
        s[i] = [(k * s[i-1] + b) mod m] + 1 + s[i-1]   for 1 <= i < n

                i  j
            [2, 4, 6] a = 15
            we've to find number of pairs whose product is <= 15



*/