#!/usr/bin/python
def sieve(n):
    is_prime = [0, 0] + [1] * (n-1)
    sq = int(n ** .5)
    for i in xrange(2, sq+1):
        if is_prime[i]:
            for j in xrange(i*i, n+1, i):
                is_prime[j] = 0
    return [i for i, p in enumerate(is_prime) if p]

from itertools import count
n = int(raw_input())
doubt = [1] + sieve(n+100)
for x in count(n-100):
    if not x in doubt:
        print x
        break