import sys


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    n = int(input())
    i = 3
    while i*i <= n:
        if n % i == 0:
            print(i)
            return
        i += 1
    if n % 2 == 0 and n > 4:
        print(n//2)
    else:
        print(n)


if __name__ == '__main__':
    main()