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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    int p,d,m,s;
    cin>>p>>d>>m>>s;
     if(s<p)
     {
         cout<< "0" << "\n";
         return 0;
     }
     s-=p;
    int cnt=1;
    while(s>=p)
    {
        cnt++;
        p-=d;
        if(p<=m)
        p=m;
        s-=p;
       
    }
    cout<< cnt << "\n";
    return 0;
}