#include <iostream>
using namespace std;
long long n,cmax,cmin,uc;
int main()
{
cin>>n;
cmax=-1;
cmin=10;
while(n!=0)
{
uc=n%10;
if(uc>cmax)cmax=uc;
if(uc<cmin)cmin=uc;
n=n/10;
}
if(cmax%2==0 && cmin%2==1)
cout<<cmax*cmin;
return 0;
}
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