'''
Problem:
A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 x 99.
Find the largest palindrome made from the product of two 3-digit numbers which is less than N.
'''
from __future__ import print_function
n = int(input().strip())
answer = 0
for i in range(999,99,-1): #3 digit nimbers range from 999 down to 100
    for j in range(999,99,-1):
        t = str(i*j)
        if t == t[::-1] and i*j < n:
            answer = max(answer,i*j)
print(answer)
exit(0)