#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,g,s,b,q,h,x;
	float p;
	cin>>n;
	g=n%10;
	s=n/10%10;
	b=n/100%10;
	q=n/1000;
	h=b+q*10;
	x=s*10+g;
	p=(n+h+x)/3.0;
	printf("%.2f",p);
}
/**************************************************************
	Problem: 1618
	User: xiaojingxuan
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/