#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,a,b,c,d,e,f;
    float z;
    cin>>n;
    a=n%10;
    b=n/10%10;
    c=n/100%10;
    d=n/1000;
    e=a*10+b;
    f=c*10+d;
    z=(n+e+f)/3.0;
    printf("%.2f",z);
}
/**************************************************************
	Problem: 1618
	User: sucongyi
	Language: C
	Result: Compile Error
****************************************************************/