#3665 cmmcp

#include <iostream>

using namespace std;

long long n;
int maxim;
int main () {
    cin>>n;
    if (n == 0) {
        cout<<0;
        return 0;
    }
    maxim = -1;
    while (n!=0) {
        if (n%2 == 0) {
            if (n%10 > maxim)
                maxim = n%10;
        }
        n /= 10;
    }
    if (maxim == -1)
        cout<<10;
    else
        cout<<maxim;

    return 0;
}