#include<bits/stdc++.h>
using namespace std;
int main() {
	int x,y;
	cin>>x>>y;
	printf("%.1f",(x-1)*2.5+y*1.5);
}
/**************************************************************
	Problem: 1603
	User: linzihang
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/