import sequtils,strutils,algorithm,math,sugar,macros,strformat
import sets,tables,intsets,queues,heapqueue,bitops
const INF = int.high div 4
proc powerWhenTooBig(x,n:int,modulo:int = 0): int =
  proc mul(x,n,modulo:int):int =
    if n == 0: return 0
    if n == 1: return x
    result = mul(x,n div 2,modulo) mod modulo
    result = (result * 2) mod modulo
    result = (result + x * (n mod 2 == 1).int) mod modulo
    if n == 0: return 1
  if n == 1: return x
  let
    pow_2 = powerWhenTooBig(x,n div 2,modulo)
    odd = if n mod 2 == 1: x else: 1
  if modulo > 0:
    const maybig = int.high.float.sqrt.int div 2
    if pow_2 > maybig or odd > maybig:
      result = mul(pow_2,pow_2,modulo)
      result = mul(result,odd,modulo)
    else:
      result = (pow_2 * pow_2) mod modulo
      result = (result * odd) mod modulo
  else:
    return pow_2 * pow_2 * odd
proc millerRabinIsPrime(n:int):bool = # O(log n)
  proc ctz(n:int):int{.importC: "__builtin_ctzll", noDecl .} # 01<0000> -> 4
  proc power(x,n:int,modulo:int = 0): int =
    if n == 0: return 1
    if n == 1: return x
    let pow_2 = power(x,n div 2,modulo)
    result = pow_2 * pow_2 * (if n mod 2 == 1: x else: 1)
    if modulo > 0: result = result mod modulo
  if n <= 1 : return false
  if n div 2 == 0: return false
  if n == 2 or n == 3 or n == 5: return true
  let
    s = ctz(n - 1)
    d = (n - 1) div (1 shl s)
  var a_list = @[2, 7, 61]
  if n >= 4_759_123_141 and n < 341_550_071_728_321:
    a_list = @[2, 3, 5, 7, 11, 13, 17]
  if n in a_list : return true
  for a in a_list:
    if powerWhenTooBig(a,d,n) == 1 : continue
    let notPrime = toSeq(0..<s).allIt(powerWhenTooBig(a,d*(1 shl it),n) != n-1)
    if notPrime : return false
  return true
proc squareFormFactor(n:int):int =
  if millerRabinIsPrime(n) : return n
  proc check(k:int):int =
    proc √(x:int):int = x.float.sqrt.int
    if n <= 1 : return n
    if n mod 2 == 0 : return 2
    if √(n) * √(n) == n : return √(n)
    var P,Q = newSeq[int]()
    block:
      P &= √(k * n)
      Q &= 1
      Q &= k * n - P[0]*P[0]
    while √(Q[^1]) * √(Q[^1]) != Q[^1]:
      let b = (√(k * n) + P[^1] ) div Q[^1]
      P &= b * Q[^1] - P[^1]
      Q &= Q[^2] + b * (P[^2] - P[^1])
    block:
      if Q[^1] == 0 : return check(k + 1)
      let
        b = (√(k * n) - P[^1] ) div Q[^1]
        P0 = b * √(Q[^1]) + P[^1]
        Q0 = √(Q[^1])
        Q1 = (k*n - P0*P0) div Q0
      (P,Q) = (@[P0], @[ Q0, Q1 ])
    while true:
      let b = (√(k * n) + P[^1] ) div Q[^1]
      P &= b * Q[^1] - P[^1]
      Q &= Q[^2] + b * (P[^2] - P[^1])
      if P[^1] == P[^2] or Q[^1] == Q[^2]: break
    let f = gcd(n,P[^1])
    if f != 1 and f != n : return f
    else: return check(k+1)
  return check(1)

proc getFactors(n:int):seq[int]=
  if n == 1 : return @[1]
  if n == 0 : return @[0]
  result = @[]
  var m = n
  while true:
    let p = m.squareFormFactor()
    if p.millerRabinIsPrime(): result &= p
    else: result &= p.getFactors()
    if p == m: return
    m = m div p


proc getchar_unlocked():char {. importc:"getchar_unlocked",header: "<stdio.h>" .}
proc scan(): int =
  while true:
    var k = getchar_unlocked()
    if k < '0' or k > '9': break
    else: result = 10 * result + k.ord - '0'.ord

let n = scan()
if n.millerRabinIsPrime(): quit $n, 0
if n mod 2 == 0:
  let factors = (n div 2).getFactors().sorted(cmp)
  if factors[0] == 2 :
    if 3 in factors : echo 3
    else: echo 4
  else: echo factors[0]
  quit 0
let factors = n.getFactors().sorted(cmp)
echo factors[0]