An integer is said to be a palindrome if it is equal to its
reverse.  For example, 79197 and 324423 are palindromes. In this task
you will be given an integer N, 1 ≤ N ≤ 1000000.  You must find
the smallest integer M ≥ N such that M is a prime number and M is a
palindrome.  
For example, if N is 31 then the answer is 101.

Input
A single integer N, (1 ≤ N ≤ 1000000), on a single line.

Output
Your output must consist of a single integer, the smallest prime
palindrome greater than or equal to N.

Example

Input:
31
Output:
101
def isprime(n):
    if n%2 == 0: return False
    if n%3 == 0: return False

    i=5
    w=2
    while i*i <=n:
        if n%i == 0:
            return False
        i+=w
        w=6-w
    return True


N = int(raw_input())
if N%2 ==0:
    N+=1

flag=0
while 1:
    if str(N) == str(N)[::-1]:
        if isprime(N):
            print N
            flag=1
    if flag:
        break
    N+=2