#include <bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
typedef pair<int,int> pi;
typedef long long ll;
std::vector<int> v;
int main(){
	//freopen("task.in","r",stdin);freopen("task.out","w",stdout);
	int p,d,m,s,ans=0,fl=0;
	cin >> p >> d>> m >>s;
	while(p>m){
		if(s>=p){
			ans++;
			s-=p;
			p-=d;
		}
		else{
			fl=1;
			break;
		}
	}
	if(s>=m && fl==0){
		ans+=s/m;
	}
	printf("%d\n",ans );
}