#include <iostream>
using namespace std;
int main() {
int n;
float par=0, impar=0;
cin>>n;
while(n!=0){
if(n%10%2==0){
par=par+n%10;
}
else{
impar=impar+n%10;
n=n/10;
cout<<par/impar;
return 0;
