#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <stdio.h>
#include <cstring>
#include <queue>
#include <stack>
#include <functional>
#include <math.h>
#include <iomanip>
using namespace std;
#define Would
#define you
const int INF = 999999999;
const int MOD = 1e9 + 7;
const double pi = 3.141592653589793238;

int main() {
	long long a, b, c, d, ans = 0;
	cin >> a >> b >> c >> d;
	while (a) {
		++ans;
		if (c <= (ans % 12) + 1 && (ans % 12) + 1 <= c + d - 1) { a -= (2 * b); }
		else { a -= b; }
	}
	cout << ans << endl;
}