#include <bits/stdc++.h>
using namespace std;

int main()
{
	int n, m, p, q;
	cin >> n >> m >> p >> q;
	int ans = 0;
	for (int i = 1; n; i = max(1, (i + 1) % 13))
	{
		n = max(0, n - ((p <= i && i <= p + q) ? 2 * m : m));
		ans++;
	}
	cout << ans << endl;
	return 0;
}