#include <bits/stdc++.h> using namespace std; int main() { int x,y; double n = 1.0; cin >> x >> y; if(x<40) { n = x*y; } else if(x>=40&&x<50) { n = 40*y+(x-40)*1.5; } else { n = 40*y+10*1.5+(x-50)*2; } printf("%.2f",n); return 0; }