#include<iostream>
using namespace std;
int main()
{
  int p,d,m,s;
  cin >> p >> d >> m >> s;
  
  int count=0;
  
  while(s>=p)
  {
    s-=p;
    
    count++;
    
    if(p-d>=m)
      p-=d;
      
    else 
      p=m;
      
  }
  
  cout << count;
}