#include <bits/stdc++.h>
using namespace std;
int main(){
    float p;
    int w,s,y;
    scanf("%d %d %d",&w,&s,&y);
    p=(w+s+y)/3.0;
    printf("%.3f",p);
}
/**************************************************************
	Problem: 1957
	User: xuezihong1
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/