#include<bits/stdc++.h>
using namespace std;
int main(){
    float g;
	int y,s,a;
	scanf("%d %d %d",&y,&s,&a);
	g=(y+s+a)/3.0;
	printf("%.3f",g);
	
}

/**************************************************************
	Problem: 1957
	User: zhengzihao3
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/