#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
int main()
{
	ll i,j=0,k,n,m,x;
	cin>>n>>m>>k>>x;
	ll p=0;
	while(x>=n)
	{
		j++;
		x=x-n;
		n=n-m;
		if(n<k)
		n=k;
		p+=1;
	}
	cout<<j;
	return 0;
}