#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<string>
#include<iostream>
#include<iostream>
#include<cctype>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include <algorithm>
#include<math.h>
#include<set>
#include<map>
#include <sstream>
#include<iomanip>
#include <ctype.h>
using namespace std;

//#include<bits/stdc++.h>

int main() {

	bool f[13] = {};
	
	int a, b, c, d;
	cin >> a >> b >> c >> d;
	int t = 1;
	int r = 0;

	for (int i = c; i < c + d; i++) {
		f[i % 12] = 1;
	}

	while (a>0) {
		if (f[t]) {
			a -= b * 2;
		}
		else a -= b;
		t++;
		r++;
		t %= 12;
	}
	cout << r << endl;

	return 0;
}