import math

n = int(input())


def isInt(n):
    return int(n) == float(n)


def MinDivisor(n):
    d = 2
    sqr = math.sqrt(n)
    if isInt(sqr):
        for d in range(d, n-1):
            if n % d == 0:
                return d
            if d > sqr:
                return d
            d += 1
        return d
    else:
        for d in range(d, n-1):
            if n % d == 0:
                return d
            d += 1
        return d


if MinDivisor(n) == n-1:
    print(n)
else:
    print(MinDivisor(n))