Игра Поле Чудес: Ошибка в работе программы

program pole4udes;
Uses crt;
Label start;
Var
a,b:integer;
mas:array [1..10] of char;
mas1:string;
zadan:string;
clovo:string;
name:string;
s:boolean;
pobeda:boolean;
bukovka:char;
len:byte;
begin
start:TextColor(10);
TextBackground(9);
Clrscr;
GotoXY(1,1);
Writeln('...');
Writeln;
Writeln;
Write('....');
Readln(zadan);
Write('...');
Readln(clovo);
Write('‚....');
Readln(name);
Clrscr;
GotoXY(1,1);
Writeln('.....');
Writeln;
Writeln;
len:=length(clovo);
Writeln('.... ',name);
Writeln('...',zadan);
Writeln('...',len,' .');
Writeln('....');
for a:=1 to length(clovo) do
mas[a]:= '*';
pobeda:=false;
while pobeda=false do
begin
GotoXY(1,10);
Write('',name,' ...');
Readln(bukovka);
mas1:='';
for a:=1 to len do
begin
if clovo[a]=bukovka then
begin
GotoXY(1,12);
Writeln('',name,'.... ',bukovka,'.',bukovka,'');
mas[a]:=bukovka;
for b:=1 to len do
if mas[b] <> '' then mas1:=mas1+mas[b];
end;
end;
GotoXY(1,14);
Writeln('..',mas1);
if mas1=clovo then
begin
GotoXY(1,16);
Writeln('',name,'.',clovo,'....');
pobeda:=true;
break;
end
else
begin
pobeda:=false;
end;
end;
readkey;
Goto start;
End.