#include<bits/stdc++.h>
using namespace std;
int main()
{
	float p;
	int a,b,c,z;
	cin>>a>>b>>c;
	z=a+b+c;
	p=z/3.0;
	printf("%.3f",p);







	return 0;
}

/**************************************************************
	Problem: 1957
	User: 21A
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/