#include<bits/stdc++.h>
using namespace std;
int main(){
	int x,y;
	float p;
	cin>>x>>y;
	p=(x-1)*2.5+y*1.5;
	printf("%.1f",p);
	return 0;
}
/**************************************************************
	Problem: 1603
	User: fuhoubin
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/