#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;
    if(s<p)
    {cout<< 0;return 0;}
        
    int count =1;
    s=s-p;
    while(s>0)
    {int ne =p-count*d;
     
       if(ne<m)
           ne=m;
     if(s<ne)
         break;
     s=s-ne;
     count++;
     
        
        
        
        
    }
    cout << count;
    return 0;
}