#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;
}