#include <bits/stdc++.h>
#include <math.h>
using namespace std;

int howManyGames(int p, int d, int m, int s) {
    if(s<p)
    {return 0;}
   int cost=p;int sum=p;
    int count=1;
   while (sum<=s && cost >=0){
       if(cost==m || cost-d < m){
           
           break;
       }  
       cost=cost-d;
       sum=sum+cost;
       count++;
           
       
   }
    count=count+ floor((s-sum)/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;
}