#include<iostream>
#include <iomanip>
using namespace std;
int main(){
	int x,y;
	cin>>x>>y;
	cout<<fixed<<setprecision(1)<<((x-1)*2.5+y*1.5)<<endl;
} 
/**************************************************************
	Problem: 1603
	User: admin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/