/def prime(a)/
/the contents of a-Array is larger than 1/
b = Array.new
k = 0
for i in 1..a.length-1
  if a[i] == 2 or a[i] == 3
    b[k] = a[i]
    k += 1
    next
  elsif a[i] % 2 != 0
    j = 3
    while a[i] % j != 0
      j += 2
      if j >= a[i]/2
        b[k] = a[i]
        k += 1
        break
      end
    end
  end
end
/print(b)/
return k
/end/

