#include <iostream>
using namespace std;
int main(){
	int p,d,m,s,z=0;
	cin>>p>>d>>m>>s;
	while(s>0){
		s=s-p;
		z++;
		if(p>m){
			p=p-d;
		}
		if(p<m){
			p=m;
		}
		//cout<<p<<" ";
	}
	if(s<0){
		cout<<z-1<<endl;
	}
	else cout<<z<<endl;
	return 0;
}