#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 count=0;
    for(;s-p>=0;){
        count++;
        s-=p;
        if(p-d>=m) p-=d;
        else p=m;
    }
    cout<<count;
    return 0;
}