procedure quick_sort(a,left,right)
begin
var integer: i,j,meta,par,app,left,right
var array of integer: a[1...n]
if(!(left<=right))then
   meta:=(left+right)/2
   par:=a[meta]
   i:=left
   j:=right
   while(i<j)do
      while(a[i]<par)do
         i:=i+1
         endwhile
      while(a[j]>par)do
         j:=j-1
         endwhile
      if(i<j)then
          app:=a[i]
          a[i]:=a[j]
          a[j]:=app
      endif
    endwhile
  if((right-j)<(j-left))then
      quick_sort(a,j+1,right)
      quick_sort(a,left,j)
  else
      quick_sort(a,left,j)
      quick_sort(a,j+1,right)
  endif
end quick_sort