#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c;
	float i=0;
	cin>>a>>b>>c;
	i=(a+b+c)/3.0;
	printf("%.3f",i);
	
}

/**************************************************************
	Problem: 1957
	User: caiqiaoxi
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/