#include<iostream>

using namespace std;

int main()
{
	int p, d, m, s;
	cin >> p >> d >> m >> s;
	int sum = 0;
	int answer = 0;
	
	while (1)
	{
		if (sum + p > s)
			break;
		answer++;
		sum += p;
		p -= d;
		if (p <= m)
		{
			p = m;
			break;
		}
	}
	answer += (s - sum) / p;
	cout << answer;
	return 0;
}