#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 k=0,sum=0;
    while(sum<=s)
    {
        sum+=p;
        k++;
        if((p-d)>m)
            p=p-d;
        else
            p=m;
    }
    cout<<k-1;
    return 0;
}