include<bits/stdc++.h>
using namespace std;
int main(){
    int x,y;
    float h;
    cin>>x>>y;
    h=(x-1)*2.5+y*1.5;
    printf("%.1f",h);
}
/**************************************************************
	Problem: 1603
	User: zhangyilei
	Language: C++
	Result: Compile Error
****************************************************************/