#include <iostream>
#include <vector>
using namespace std;

int main()
{
	ios_base::sync_with_stdio( false );
	cin.tie( nullptr );
	int res = 0;
	int p, d, m, s;
	cin >> p >> d >> m >> s;
	while ( s - p >= 0 )
	{
		++res;
		s -= p;
		p -= d;
		if ( p < m )
			p = m;
	}
	cout << res << '\n';
	
}