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

int main()
{
	int N, M, P, Q;
	cin >> N >> M >> P >> Q;

	int ans = 1;
	while( true ) {
		int mm = (ans - 1) % 12 + 1;
		if( P <= mm && mm <= P + Q - 1 ) N -= M * 2;
		else N -= M;
		if( N <= 0 ) break;
		ans++;
	}

	cout << ans << endl;
}