import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		long n = in.nextLong();
 
		System.out.println(f(n));
	}
	
	static long f(long n)
	{
		if(n < 10)
			return n;
		long sum=1;
		while(n>0)
		{
			if(n%10!=0)
				sum*=n%10;
			n/=10;
		}
		return f(sum);//4018224312
	}
 
} 
/**************************************************************
	Problem: 1846
	User: admin
	Language: Java
	Result: Accepted
	Time:4095 ms
	Memory:40528 kb
****************************************************************/