

program quicksort;

const n=31;

var a: array [1..n] of integer;

procedure aswap (i, j: integer);
var t : integer;
begin
     t := a[i];
     a[i] := a[j];
     a[j] := t;
end;

procedure swap (var a, b: integer);
var t : integer;
begin
     t := a;
     a := b;
     b := t;
end;

procedure quick (r, s: integer);
var i, k, x: integer;
begin
    i := r;
    k := s;
    x := a[(i+k) div 2];
    repeat
         while a[i] < x do i:= i+1;
         while a[k] > x do k:=k-1;
         if i<=k then begin
                       aswap (i,k);
                       i:=i+1;
                       k:=k-1;
                    end;
    until i>k;
    if r a[i+1]then
         ok:=false;
    if not ok then
         writeln('Chyba');
end;

begin
     fill;
     print;
     quick (1, n);
     print;
     check;
     readln;
end.