#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int p,d,m,s,r;
    cin>>p>>d>>m>>s;
  r=0;
    while(s>0)
    {
       s=s-p;
        p=p-d;
    if(p<m)
    {
        p=m;
    }
    r++;
    }
    if(s==0)
    {
        cout<<r;
    }
    if(s<0)
    {
        cout<<r-1;
    }
    
    return 0;
}