prod_pi

#include <iostream>
using namespace std;

int main()
{
    int n;
    cin>>n;
    int MIN=9,MAX=0;
    while(n)
    {
        if(n%10%2==0&&n%10>MAX)
            MAX=n%10;
        if(n%10%2&&n%10<MIN)
            MIN=n%10;
        n/=10;
    }
    cout<<MIN*MAX;
    return 0;
}