#include<bits/stdc++.h>
using namespace std;
int main(){
    float p;
    int a,b,c,z;
    cin>>a>>b>>c;
    z=a+b+c;
    p=z/3.0;
    printf("%.3f",p);
    return 0;
}
/**************************************************************
	Problem: 1957
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/