#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a,b,c,d,e,f,x,x2;
	float h;
	cin>>n;
	a=n%10;
	b=n/10%10;
	c=n/100%10;
	d=n/1000;
	e=a+b*10;
	f=c+d*10;
	h=(e+f+n)/3.0;
	printf("%.2f",h);
	return 0;
}

/**************************************************************
	Problem: 1618
	User: tangkaixuan
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/