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