#include<bits/stdc++.h>
using namespace std;
int main(){
	int w,s,y;
	float p;
	scanf("%d %d %d",&w,&s,&y);
	p=(w+s+y)/3.0;
	printf("%.3f",p);
}
/**************************************************************
	Problem: 1957
	User: sucongyi
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/