divisor n p | p>ceiling(sqrt (fromIntegral n)) = [n]
            | True = if n`mod`p==0 then p:(divisor (n`div`p)(p+1)) else divisor n (p+1)

main=do
    n<-getLine>>=return.(read::String->Integer)
    let a = take 2 $ divisor n 2
    print$if a!!0==2 then a!!1 else a!!0