#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c,d,e,f,g;
	float h;
	cin>>a;
	b=a%10;
	c=a/10%10;
	d=a/100%10;
	e=a/1000%10;
	f=b+c*10+d+e*10;
	g=a+f;
	h=g/3.0;
	printf("%.2f",h);
}
/**************************************************************
	Problem: 1618
	User: toughuatao1
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/