PROCEDURE ADDHEAP(HEAD,TAIL:INTEGER);
    VAR MIN,W:INTEGER;
    BEGIN
      IF 2*HEAD>TAIL THEN MIN:=-1
      ELSE IF 2*HEAD=TAIL THEN MIN:=TAIL
      ELSE IF A[2*HEAD]>A[2*HEAD+1]
              THEN MIN:=2*HEAD+1 ELSE MIN:=2*HEAD;
      IF (MIN>0) AND (A[HEAD]>A[MIN]) THEN BEGIN
         W:=A[HEAD];
         A[HEAD]:=A[MIN];
         A[MIN]:=W;
         ADDHEAP(MIN,TAIL)
        END
  END;
  PROCEDURE MAKEHEAP(HEAD,TAIL:INTEGER);
    VAR X:INTEGER;
    BEGIN
      X:=(TAIL DIV 2)+1;
      WHILE X>HEAD DO
        BEGIN
          X:=X-1;
          ADDHEAP(X,TAIL)
        END
     END;
  PROCEDURE QSORT2 (FWARD,BWARD:RANGE);
    VAR MAE,USIRO:RANGE;
        NAKA,W:INTEGER;
    BEGIN
      MAE:=FWARD;
      USIRO:=BWARD;
      NAKA:=A[(MAE+USIRO) DIV 2];
      IF USIRO-MAE<M THEN MAKEHEAP(1,N);
      REPEAT
        WHILE A[MAE]<NAKA DO MAE:=MAE+1;
        WHILE A[USIRO]>NAKA DO USIRO:=USIRO-1;
        IF MAE<=USIRO THEN BEGIN
          W:=A[MAE];
          A[MAE]:=A[USIRO];
          A[USIRO]:=W;
          MAE:=MAE+1;
          USIRO:=USIRO-1
        END ;
      UNTIL MAE>USIRO;
      IF USIRO>FWARD THEN QSORT2 (FWARD,USIRO);
      IF MAE<BWARD THEN QSORT2 (MAE,BWARD)
    END;
  PROCEDURE INIT;
    VAR I:INTEGER;
    BEGIN
      FOR I:=1 TO N DO
        A[I]:=0
    END;