#!/usr/bin/python
from collections import defaultdict

def factorize(n):
    res = defaultdict(int)
    d = 2
    while d * d <= n:
        while n % d == 0:
            res[d] += 1
            n /= d
        d += 1
    if n > 1:
        res[n] += 1
    return res

n = int(raw_input())
arr = filter(lambda x: x>2, sorted(factorize(n).keys())) or [n]
res = arr.pop()
print res