#include <iostream>

int main() {
    int n, m, p, q;
    int x = 1;
    int w = 0;
    std::cin >> n >> m >> p >> q;
    while (n > 0) {
        if (x >= p && x <= p + q - 1) {
            n = n - (m * 2);
        }
        else {
            n -= m;
        }
        x++;
        w++;
        if (x >= 13) x = 1;
    }
    std::cout << w << std::endl;
}