#include <iostream>
#include <cstdio>
#include <vector>
#include <map>
#include <queue>
#include <string>
#include <algorithm>

#define REP(i, n) for(ll i = 0; i < (n); i++)
#define INF 1e16
#define MOD 1e9 + 7

using namespace std;
using ll = long long;



int main() {
	ll a, b, c, d;
	cin >> a >> b >> c >> d;
	ll ans = 0, sum = 0, c1 = 0, c2 = 0;
	while (1) {
		if (sum + 1 + c <= d && c1 < a && c2 < b) {
			sum += 1 + c;
			c1++;
			c2++;
			ans++;
		}
		else {
			break;
		}
	}
	cout << ans << endl;
}