#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 cnt = 0;
    while (s >= m) {
        s -= p;
        p -= d;
        p = max(p, m);
        cnt ++;
    }
    if (s < 0) cnt--;
    cout << cnt << endl;
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}