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