#include <bits/stdc++.h>
using namespace std;
#define lint long long int
int main()
{
	lint p,d,m,s;
	cin>>p>>d>>m>>s;
	lint ss=0,c=0;
	while(1)
	{
		ss+=p;
		if(ss>s)
			break;
		else
		{
			c++;
			if(p-d>m)
				p=p-d;
			else
				p=m;
		}
	}
	cout<<c<<"\n";


}