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

int main() {
	int n, m, p, q; cin >> n >> m >> p >> q;
	vector<bool> v(13, false);
	for (int i = 0; i < q; ++i) {
		v[p+i] = true;
	} 
	int count = 0; int month = 1;
	while (n > 0) {
		count++;
		n -= m;
		if (v[month]) n -= m; 
		month++;
		if (month > 12) month -= 12;
	}
	cout << count << endl;
	return 0;
}