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