program frecur( output );    var	time : integer;	direction : integer;    function pad( j : integer ) : integer;	const	    indent = 4;	begin	    {}	    if ( j <= 0 ) then begin		j := 1;	    end;	    {}	    pad := j * indent;	end;    procedure a( procedure xx );	begin	    writeln( ' ':pad(time) , 'a: about to	xx()' );	    xx;	    writeln( ' ':pad(time) , 'a: back from	xx()' );	end;    procedure b( procedure yy );	procedure c;	    begin		writeln( ' ':pad(time) , 'c: about to	a(yy)' );		time := time + direction;		a( yy );		writeln( ' ':pad(time) , 'c: back from	a(yy)' );	    end;	begin	    if ( direction = 1 ) then begin		if ( time > 10 ) then begin		    direction := -direction;		end;		time := time + direction;		writeln( ' ':pad(time) , 'b: about to	b(c)' );		b( c );		writeln( ' ':pad(time) , 'b: back from	b(c)' );	    end else begin		writeln( ' ':pad(time) , 'b: about to	yy' );		yy;		writeln( ' ':pad(time) , 'b: back from	yy' );	    end;	end;	procedure d;	    begin		writeln( 'd:' );	    end;    begin	time := 1;	direction := 1;	writeln( 'program: about to	b( d )' );	b( d );	writeln( 'program: back from	b( d )' );    end.