#include "bits/stdc++.h"

using namespace std;

using ll = long long;
using ld = long double;

const double PI = 3.1415926535897932384626433832795;

const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { -1, 0, 1, 0 };

int gcd(int x, int y) { return y ? gcd(y, x % y) : x; }
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
int lcm(int x, int y) { return x / gcd(x, y) * y; }
ll lcm(ll x, ll y) { return x / gcd(x, y) * y; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	int n, m, p, q;
	cin >> n >> m >> p >> q;

	int ans = 0, now = 1;
	for (int life = n; life > 0; now = now < 12 ? now + 1 : 1) {
		life -= p <= now && now < p + q ? 2 * m : m;
		ans++;
	}

	cout << ans << endl;
	return 0;
}