#!/usr/bin/python

import sys;
import math;
import os

def nDigitProduct(num,offset,digits):

	sum = 1;
	for i in range(offset,offset+digits):
		sum *= int(num[i]);

	return sum;

def greatestProduct(num,digits):

	higherProduct = 0;
	for i in range (0, len(num)-(digits-1)):
		product = nDigitProduct(num,i,digits);
		if(product > higherProduct):
			higherProduct = product;

	return higherProduct;

strNum = "".join(sys.stdin.readlines()).replace('\n','')
numDigits = int(sys.argv[1])
print "Result is: " + str(greatestProduct(strNum,numDigits));