#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    // Return the number of games you can buy
   long long  int sum=0;
    int count =0;
   long long  int price =p;
    while(s>=price )
     {
       
        s=s-price;
        sum=sum+price;
        count++;
        price=price-d;
         if(price<=m )
        {
            price=m; 
        }
        
       // s-=price;
        
     }
   //  cout<<sum;
    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;
}