import math
import sys
sys.setrecursionlimit(100000)

def isPrime(n):
    if n % 2 == 0 : return False
    for i in range(3,int(math.sqrt(n)),2):
        if n % i == 0:
            return False
    return True

if __name__ == "__main__":
    N = int(input())
    if isPrime(N) == True:
        print(N,"\n")
    else:
        for i in range(3,int(math.sqrt(N))):
            if N % i == 0:
                print(i,"\n")
                break