#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s)
{
  int count;  
  for(int i=s;i-p>=0;)
  {
    i=i-p;
    count++;  
    p=p-d;
    if(p<m)
    {
      p=m;  
    }
  }
   return count;   
}

int main() {
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    int answer = howManyGames(p, d, m, s);
    cout << answer << endl;
    return 0;
}