#include<bits/stdc++.h>
using namespace std;
int main(){
	float a,b,c,p;
	cin>>a>>b>>c;
	p=(a+b+c)/3;
	printf("%.3f",p);
}
/**************************************************************
	Problem: 1957
	User: toughuatao1
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/