#include <stdio.h>
int main()
{
int greatest=0,t;
char a[1100];
int d[1100],i;
scanf("%s",a);
for (i=0;i<4;++i)
d[i]=a[i]-'0';
for (i=4;a[i];++i){
d[i]=a[i]-'0';
t=d[i]*d[i-1]*d[i-2]*d[i-3]*d[i-4];
if (t>greatest)
greatest=t;
}
printf("%d\n",greatest);
return 0;
}