def qsort(a):
 if len(a)<2:
  return

 left,right=0,len(a)-1
 el = a[right//2]

 while left <= right:
  while a[left]<el:
   left+=1

  while a[right]>el:
   right-=1

  if left<=right:
   a[left],a[right] = a[right],a[left]
   left+=1
   right-=1

  qsort(a[left:])
  qsort(a[:right])

a=[10,9,8,7,6,4,3,2,1]
qsort(a)
print a