#include <bits/stdc++.h>

using namespace std;

int main() {
    int m, p, d, s;
    
    cin >> p >> d >> m >> s;
    
    int ans = 0;
    int price = p;
    
    while (0 <= s - price) {
        ans++;
        
        s -= price;
        
        if (m < price) price = max(price - d, m);
        else price = m;
    }
    
    cout << ans << endl;
    
    return 0;
}