#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 sum=0;
    int count=-1;
    while(sum<=s){
        if(p>=m){
            sum+=p;
            p=p-d;
        }
        else{
            sum+=m;
        }
        //cout << sum << endl;
        count++;
    }
    cout << count << endl;
    return 0;
}