#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
int main(){
	
	int t;
	//cin >> t;
	//while(t--)
    {
	int p,d,m,s;
	cin >> p >> d >> m >> s;
	if(s<p){
	
	cout <<"0\n";
	return 0;
}
int sum=0,cnt=0;
while(p>=m){
//	cout << p << " ";
	sum+=p;
	if(sum>s)
	break;
	p=p-d;
	cnt++;
}
if(s>sum){
	s=s-sum;
	cnt+=s/m;
}
cout << cnt << endl;

	}
	
	
	return 0;
}