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

int main()
{
	int p,d,m,s,n,i,k,l,x;

	scanf("%d%d%d%d", &p,&d,&m,&s);

	x = p;
	k = 0;
	l = 4;
	while(x>=m && s>=0)
	{
		s -= x;
		x -= d;
		

		k++;
		// cout<<" s = "<<s<<" k = "<<k<<endl;
	}

	k--;
	if(s!=0)
	{
		while(s>=0)
		{
			s -= m;
			k++;
			// cout<<" s = "<<s<<" k = "<<k<<endl;
		}
	}
	

	printf("%d\n", k);

	
	return 0;
}