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


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