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

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