#include <bits/stdc++.h>
using namespace std;

int main()
{
    int a, b, c, d; cin >> a >> b >> c >> d;
    int res = 0;
    while(1)
    {
        if(a > d) break;
        res++;
        d -= a;
        a = max(a-b, c);
    }

    cout << res << endl;
}