import math

x = input()

def isPrime(n):
  if n < 2:
    return 0
  elif n == 2:
    return 1
  for i in range(2, int(math.sqrt(n))+1):
    if not n % i:
      return 0
  return 1

d=[-1,-1,-1,-1,3,-1,5,-1,7,7,7,-1,11,-1,13,7,7,-1,8,-1,19,19,7,-1,23,23,8,8,8,-1,8,-1,8,8,8,8,8,-1,8,8,8,-1,8,-1,8,8,8,-1,8,14,8,8,8,-1,8,8,8,8,8,-1,8,-1,8,8,8,8,8,-1,8,8,8,-1,8,-1,8,8,8,8,8,-1,8,14,8,-1,8,8,8,8,8,-1,8,8,8,8,8,8,8,-1,8,8]

if x < 100:
    print d[x]
else:
    a = x-1
    b = x-8
    flag = 0
    if a%8!=0:
        flag = 1
    for i in xrange(30000):
        if isPrime(i)==1:
            if b%i==0:
                flag = 1
                break
    if flag == 0:
        print 14
    else:
        print 8