#include<bits/stdc++.h>
using namespace std;
int x,y;
double h;
int main(){
	cin>>x>>y;
	x--;
	h=x*2.5+y*1.5;
	cout<<fixed<<setprecision(1)<<h;
}

/**************************************************************
	Problem: 1603
	User: zhangziang
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/