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


int main() {
    int p, d, m, s, ctr = 0;
    cin >> p >> d >> m >> s;
    while (s > 0) {
        s -= p;
        p -= d;
        if (p < m) p = m;
        if (s >= 0) ++ctr;
    }
    cout << ctr << '\n';
    return 0;
}