from random import randrange
from queue import Queue

def is_prime( n ):
  if n <= 1 or ( n > 2 and ~n & 1 ): return False
  if n == 2 or n == 3: return True
  for i in range( 100 ):
    a = randrange( 2, n - 1, 1 )
    p = n - 1
    if pow( a, p, n ) != 1: return False
    while ~p & 1:
      x = pow( a, p, n )
      if x != 1 and x != n - 1: return False
      p >>= 1
  return True

N = int( input() )

if N < 100:
  for w in range( 1, N + 1, 1 ):
    dd = [ -1, 1, -w, w ]
    vis = [ False for i in range( N + 1 ) ]
    que = Queue()
    vis[ 1 ] = True
    que.put( 1 )
    while not que.empty():
      u = que.get()
      if u == N:
        exit( print( w ) )
      for di in range( 4 ):
        nu = u + dd[ di ]
        if not ( 1 <= nu and nu <= N ): continue
        if is_prime( nu ): continue
        if vis[ nu ]: continue
        vis[ nu ] = 1
        que.put( nu )

else:
  if N % 8 != 1 or not is_prime( N - 8 ):
    print( 8 )
  else:
    print( 14 )