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


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