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