#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
   int sum=0,c=0;
    while(1)
   {
       if(sum+p>s)
       {break;
           
       }
       sum+=p;
        
       p=p-d;
        if(p<m)
            p=m;
       // printf("%d ",p);
        if(sum<=s)
        c++;
   }
    return c;
    // Return the number of games you can buy
}

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;
}