#include <bits/stdc++.h> using namespace std; int main() { int a,b; cin>>a>>b; double sum = 0; if(a <= 40) { sum = a*b; cout<<setprecision(2)<<fixed<<sum<<endl; } else if(a > 40 && a <= 50) { sum = 40*b+(a-40)*(b*1.5); cout<<setprecision(2)<<fixed<<sum<<endl; } else if(a > 50) { sum = 40*b+10*(b*1.5)+(a-50)*(b*2); cout<<setprecision(2)<<fixed<<sum<<endl; } return 0; }