import math

def cnv(N):
    for n in range(3, int(math.sqrt(N)) + 1):
        if N % n == 0:
            return n
    if N % 2 == 0:
        return N // 2
    else:
        return N

def main():
    N = int(input())
    print(cnv(N))

if __name__ == '__main__':
    main()