#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
   	int count=0,flag=0;
 	while((s>=p)&&(s>(m-1)))
 	{
 		count++;
 		s-=p;
 		if(!flag)
 		p-=d;
 		if(p<m)
 		{
 			p=m;
 			flag=1;
 		}
	}
	return count; // 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;
}