#include<bits/stdc++.h>
using namespace std;
int main(){
    int x,y;
    float q; 
	cin>>x>>y;
	q=(x-1)*2.5+y*1.5;
	printf("%.1f",q); 
}
/**************************************************************
	Problem: 1603
	User: xuezihong1
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/