#include <bits/stdc++.h>
using namespace std;
int main(){
   int a;
   float b,c,d,e,m;
   cin>>a;
   b=a%10;
   c=a/10%10;
   d=a/100%10;
   e=a/1000;
   m=(a+b+c*10+d*1+e*10)/3.0;
   cout<<m;					
} 
/**************************************************************
	Problem: 1618
	User: tonghuawei
	Language: C++
	Result: Wrong Answer
****************************************************************/