#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int p, d, m, s;
    cin >> p >> d >> m >> s;
    int sum = 0;
    while (s > 0)
    {
        if (s >= p)
            s -= p, ++ sum;
        else
            s = 0;
        p = max (p - d, m);
    }
    cout << sum;
    return 0;
}