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

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