#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, ans=0, tot=0;
    cin >> p >> d >> m >> s;
    while(tot<=s)
    {
        tot+= p;
        if (p-d>=m) p -=d; else p = m;
        ans++;
    }
    cout << ans-1;
    return 0;
}