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