def quicksort(list_,start,end):
if start>=end:
return
left=start
right=end
mid=list_[start]
while left<right:
while left<right and list_[right]>=mid:
right-=1
list_[left]=list_[right]
while left <right and list_[left]<mid:
left+=1
list_[right]=list_[left]
list_[left]=mid
quicksort(list_,start,left-1)
quicksort(list_,left+1,end)
list1= [54, 26, 93, 17, 77, 31, 44, 55, 20]
quicksort(list1,0,len(list1)-1)
print(list1)