#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c;
	double n=0;
	cin>>a>>b>>c;
	printf("%.3f",n=(a+b+c)/3);
	cout<<n;
	return 0;
}
/**************************************************************
	Problem: 1957
	User: lijinkai
	Language: C++
	Result: Wrong Answer
****************************************************************/