N = int(input())
sqrtN = int(N ** 0.5)
for d in range(3, sqrtN + 1):
    if N % d == 0:
        print(d)
        break
else:
    if N == 4:
        print(N)
    elif N % 2 == 0:
        print(N // 2)
    else:
        print(N)