#include <iostream>

int main()
{
	int N, M, P, Q;
	std::cin >> N >> M >> P >> Q;
	int now = 0;
	int blow = 0;

	while (N > 0)
	{
		N -= M;
		if ((now % 12) + 1 == P)
		{
			blow = Q;
		}
		if (blow > 0)
		{
			blow--;
			N -= M;
		}
		now++;
	}

	std::cout << now << std::endl;

	return 0;
}