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

int main()
{
    int n, m, p, q, i = 0;
    cin >> n >> m >> p >> q;
    while (n > 0) {
        i++;
        int month = i % 12 == 0 ? 12 : i % 12;
        if (month >= p && month < p + q) {
            n -= 2 * m;
        } else {
            n -= m;
        }
    }
    cout << i << endl;
}