#include<bits/stdc++.h>
using namespace std;
int main() {
	int x,y;
	float h;
	cin>>x>>y;
	x--;
	h=x*2.5+y*1.5;
	printf("%.1f",h);
}

/**************************************************************
	Problem: 1603
	User: chenjunlin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/