#include<bits/stdc++.h>
using namespace std;
double h,s,v,l,k,q,p;
int n;
int main(){
    cin>>h>>s>>v>>l>>k>>n;
    cout<<min(n,int(s-(sqrt((h)/5)*v+l)))-max(0,int(s-(sqrt(h-k/5))*v));
}