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