#include<bits/stdc++.h>
using namespace std;
float z;
int x,y;
int main(){
    cin>>x>>y;
    z=(x-1)*2.5+y*1.5;
    printf("%.1f",z);
}
 
/**************************************************************
	Problem: 1603
	User: chenyichuen
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/