import math


def main():
    n = int(input())
    if n > 10 and n % 2 == 0:
        n //= 2
    for i in range(3, int(math.sqrt(n)) + 3):
        if n % i == 0:
            print(i)
            return
    print(n)

if __name__ == '__main__':
    main()