#include<iostream>

using namespace std;

int main(){
	int p,d,m,s;
	cin>>p>>d>>m>>s;
	int ans = 0;
	while(s>0){
		if(s-p < 0)
			break;
		
		s = s - p;
		if(p > m)
			p = p - d;
		if(p < m)
			p = m;
		ans++;
		//cout<<p<<" "<<s<<endl;
	}
	cout<<ans<<endl;
	return 0;
}