#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 c=0;
    int x = p;
    while(s-p>=0){
        s = s-p;
        c++;
        p = p-d;
        if(p<m){
            p = m;
        }
    }
    cout<<c;
    return 0;
}