#include<bits/stdc++.h>
using namespace std;
int main(){
	int x,y,z;
	float p=0;
	cin>>x>>y>>z;
	p=(x+y+z)/3.000;
	printf("%.3f",p); 
}
/**************************************************************
	Problem: 1957
	User: chenjunlin
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/