#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 ans = 0;
    int cost = p;
    
    while (s >= cost)
    {
        ans++;
        s -= cost;
        cost -= d;
        if (cost < m)
            cost = m;
    }
    
    cout << ans << endl;
    
    return 0;
}