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 H[2*HEAD]>H[2*HEAD+1]
                          THEN MIN:=2*HEAD+1 ELSE MIN:=2*HEAD;
                  IF (MIN>0) AND (H[HEAD]>H[MIN]) THEN
                     BEGIN W:=H[HEAD];    H[HEAD]:=H[MIN];
                           H[MIN]:=W;
                           ADDHEAP(MIN,TAIL)
                     END
  END;
  PROCEDURE HEAP(HEAD,TAIL:INTEGER;H:HH);
            VAR X:INTEGER;
            BEGIN X:=(TAIL DIV 2)+1;
                  WHILE X>HEAD DO
                  BEGIN X:=X-1;     ADDHEAP(X,TAIL) END
  END;
  PROCEDURE INIT;
            VAR I:INTEGER;
            BEGIN
                  FOR I:=1 TO N DO
                       H[I]:=0
                  END;