#include<bits/stdc++.h>
using namespace std;
int main()
{
	int p,q,d,m,s;
	int g=0;
	cin>>p>>d>>m>>s;
	int sum=0;
	if(p>s)
	{
		cout<<"0";
		return 0;
	}
	else
	sum=sum+p;
	while(sum<=s)
	{
		g++;
		
		if((p-d)<=m)
		p=m;
		else
		p=p-d;
		
		sum=sum+p;
		
	}
	cout<<g;
}