#include <iostream>
#include <iomanip>
using namespace std;

int main(){
	double x,y,z;
	cin>>x>>y>>z;
	cout<<fixed<<setprecision(1)<<8.5*x+5.6*y+6.2*z;
}


/**************************************************************
	Problem: 1610
	User: admin
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/