#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;
    while (s >= p)
    {
        ans++;
        s -= p;
        if (p-d <= m)
            p = m;
        else
            p -= d;
    }
    cout<<ans<<"\n";
}