#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

unsigned int cur = 0;
unsigned int nextRand(int a, int b)
{
    cur = cur * a + b;
    return cur >> 8;
}
int inverse(vector<int> &mas)
{
    int sum = 0;
    for (int i = mas.size()-1; i > 0; --i)
    {
        for (int j = 0; j < i; ++j)
        {
            if (mas[j] > mas[i])
                sum++;
        }
    }
    return sum;
}
int main() {
    //ifstream in("invcnt.in");
    //ofstream out("invcnt.out");
    int n, m, a, b;
    cin >> n >> m >> a >> b;
    vector <int> mas(n);
    for (int i = 0; i < n; i++)
        mas[i] = (int)nextRand(a, b) % m;
    cout << inverse(mas);
    return 0;
}