import java.util.Scanner;
public class Main{
public static void main (String[] args){
	Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();			
		double m = sc.nextDouble();
		    double s = 0.0;
		    if(n <= 40) {
		        s = n * m;
		    }else if(n <= 50 && n > 40) {
		        s = m * 40 + (n - 40) * m * 1.5;
		    }else if(n > 50) {
		        s = m * 40 + 10 * m * 1.5 + (n - 50) * 2 * m;
		    }
		    System.out.println(String.format("%.2f",s));
		
	 }
		
				
     }
/**************************************************************
	Problem: 1860
	User: admin
	Language: Java
	Result: Accepted
	Time:4375 ms
	Memory:41152 kb
****************************************************************/