/* |-_-| */
#include <bits/stdc++.h>
using namespace std;

typedef long long int ll;

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	ll p, m, d, s;
	cin >> p >> d >> m >> s;

	ll count = 0;
	while(p > m && s > 0) {
		if(s >= p) {
			s -= p;
			p -= d;
			count++;
		}
    else break;
	}
	
	if(s >= m && p <= m) {
		count += s/m;
	}
	cout << count << "\n";
	return 0;
}