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