#include <bits/stdc++.h>

using namespace std;


int main() {
    int p;
    int d;
    int m;
    int s;
    int i=1,count=0;
    
    cin >> p >> d >> m >> s;
    int n=p;
   while(s>=p)
   {  
    
       if((n-d*i)>=m)
       {
           p=p+(n-d*i);
       }
    else
    {
        p=p+m;
    }
       count++;
    i++;
    
   }
    cout<<count<<endl;
    return 0;
}