import math


def main():
    n = int(input())
    if n % 2 == 0:
        n //= 2
    ans = n
    for i in range(2, int(math.sqrt(n)) + 3):
        if n % i == 0:
            ans = i
            break

    print(4 if ans == 2 else ans)

if __name__ == '__main__':
    main()