include<bits/stdc++.h>

using namespace std; int main() { //freopen("rice.in","r",stdin); //freopen("rice.out","w",stdout); double n,m; cin>>n>>m; if(n-m*5.8>=0){

printf("%.1lf",n-m*5.8);

} else{

printf("%.1lf",m*5.8-n);

} return 0; }