#include<bits/stdc++.h>
using namespace std;
int main(){
	float x,y,z,p;
	cin>>x>>y>>z;
	p=8.5*x+5.6*y+6.2*z;
	printf("%.1f",p);
	return 0;
}
/**************************************************************
	Problem: 1610
	User: xiaojingxuan
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/