#include <bits/stdc++.h>
using namespace std;

int main()
{
	int p,d,m,s;
	cin >> p >> d >> m >> s;
	int count =0;
	int val=0;
	while(1)
	{
		if(p>s)
			break;
		count += p;
		if((p-d)>=m )
			p -= d;
		else
			p = m;
		if(count>s)
			break;
		val++;
	}
	cout << val << endl;
	return 0;
}