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



/**************************************************************
	Problem: 1603
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/