program main
  implicit none
  integer*8::N,i,j,prime,total
  integer*8,allocatable::PrimeList(:)
  integer*8,allocatable::dp(:)
  read *,N
  allocate(dp(1:N))
  dp = 0
  total = 0

  call get_prime(PrimeList, N)
  do i=1 ,size(PrimeList)
     prime = PrimeList(i)
     total = prime + total
     do j=MIN(N-prime,total),1,-1
        if(dp(j) /= 0) then
           dp(j+prime) = MAX(dp(j) + 1,dp(j+prime))
        end if
     end do
     if(dp(prime) == 0) then
        dp(prime) = 1
     end if
  end do
  if(dp(N)==0) dp(N)=-1
  print '(i0)',dp(N)

contains
  subroutine get_prime(PrimeList, N)
    implicit none
    integer*8::i,j,N
    integer*8,parameter::prime=1,nonprime=0
    integer*8,allocatable::isPrime(:), PrimeList(:)
    integer*8,allocatable::numlist(:)

    allocate(numlist(N))
    allocate(isPrime(N))

    isPrime=prime
    isPrime(1)=nonprime
    isPrime(2)=prime

    do i=2, FLOOR(SQRT(REAL(N)))
       if(isPrime(i).eq.prime) then
          do j=i+i, N, i
             isPrime(j) = nonprime
          end do
       end if
    end do

    numlist=(/(i,i=1,N)/)
    PrimeList=pack(numlist,isPrime(numlist).eq.prime)
  end subroutine get_prime
end program main