#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
 long int sum;
    int i=0;
    while((sum+p)<=s)
   {sum=sum+p;
       if((p-d)>=m)
   p=p-d;
   else
   p=m;
   i=i+1;}
    return i;
}

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;
}