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