program answer
  implicit none
  integer(8) :: i, K, a
  read(*,*) k

  if(k==1) then
     write(*,*) '1'
     stop
  else if(k==3) then
     write(*,*) '3'
     stop
  else if(mod(k,5)==0) then
     write(*,*) '-1'
     stop
  else if(k==7) then
     write(*,*) '1'
     stop
  else if(mod(k,2)==0) then
     write(*,*) '-1'
     stop
  end if
 do i = 1, 12
     if(mod(7*(10**i-1)/9,K)==0) then
        write(*,*) i
        stop
     end if
  end do

  a=0
  do i = 3, int(sqrt(dble(K)))+1, 2
     if(mod(K,i)==0) then
	a=i
        exit
     end if
  end do

  if(a==0) then
     write(*,*) k-1
     stop
  end if
 stop
 end program answer
