#include<bits/stdc++.h> 
using namespace std;
int main(){
	int x,s,a,b,c,d;
	cin>>x;
	a=x%10;
	b=x/10%10;
	c=x/100%10;
	d=x/1000;
	s=b*10+a+d*10+c+x;
	printf("%.2f",s/3.0);
	
}
/**************************************************************
	Problem: 1618
	User: lvrenxiang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/