#include<bits/stdc++.h>
using namespace std;
int main(){
    int score1,score2,score3;
    scanf("%d %d %d",&score1,&score2,&score3);
    double average = (score1 + score2 + score3)/3.0;
	printf("%3f\n",average);
	
	return 0; 
}
	
/**************************************************************
	Problem: 1957
	User: huanghao
	Language: C++
	Result: Wrong Answer
****************************************************************/