#include <iostream>
#include <vector>
#include <map>
#include <set>

int main()
{
	int p, d, m, s;
	std::cin >> p >> d >> m >> s;

	int pieces = 0;
	while (true)
	{
		if (p > s)break;

		s -= p;
		++pieces;
		if (p > m)
		{
			p -= d;
            if(p<m)p=m;
		}
	}

	std::cout << pieces << std::endl;

	return 0;
}