Đổi tiền ra chữ viết bằng Pascal

uses crt; var    a:array[1..9] of string[5];    so:real;    ty,trieu,tram,nghin:0..999;    cty,ctrieu,ctram,cnghin:string[3];    chuso:string;    cso:string[30];    loi,l:integer;    tiep:char; Function doichu(n:integer):string;          var             chu:string;             tram,chuc,donvi:0..9;          begin               tram:=n div 100;               chuc:=(n-tram*100) div 10;               donvi:=n-tram*100-chuc*10;               chu:=``;               If tram<>0 Then                  chu:=chu+a[tram]+` tram`               Else                   chu:=chu+` khong tram`;               Case chuc of                    1:chu:=chu+` muoi`;                    0:if donvi<>0 then chu:=chu+` le`;                      else chu:=chu+a[chuc]+` muoi`;               End;{case}               Case donvi of                    1:if (chuc<>1) and (chuc<>0) then chu:=chu+` mot`                      else chu:=chu+ a[donvi];                    5:if chuc<>0 then chu:=chu+` lam`                      else chu:=chu+a[donvi];                    else{case}                        IF donvi<>0 then chu:=chu+ a[donvi];               End;{case}               doichu:=chu;          end;{doichu} BEGIN      a[1]:=` mot`;      a[2]:=` hai`;      a[3]:=` ba`;      a[4]:=` bon`;      a[5]:=` nam`;      a[6]:=` sau`;      a[7]:=` bay`;      a[8]:=` tam`;      a[9]:=` chin`;      Repeat            clrscr;            Write(`Nhap so: `);readln(so);            if so=0 then chuso:=`Khong dong`            else                begin                     chuso:=``;                     str(so:12:0,cso);                     ctram:=copy(cso,10,3);                     cnghin:=copy(cso,7,3);                     ctrieu:=copy(cso,4,3);                     cty:=copy(cso,1,3);                     val(cty,ty,loi);                     val(ctrieu,trieu,loi);                     val(cnghin,nghin,loi);                     val(ctram,tram,loi);                     if ty<>0 then chuso:=chuso+doichu(ty)+` ty`;                     if (ty<100) and (ty>=10) then delete(chuso,1,11);                     if ty<10 then delete(chuso,1,14);                     if trieu<>0 then chuso:=chuso+doichu(trieu)+` trieu`;                     if (ty=0) and (trieu<100) and (trieu>=10) then delete(chuso,1,11);                     if (ty=0) and (trieu<10) then delete(chuso,1,14);                     if nghin<>0 then chuso:=chuso+doichu(nghin)+` nghin`;                     if (ty=0) and (trieu=0) and (nghin<100) and (nghin>=10) then                               delete(chuso,1,11);                     if (ty=0) and (trieu=0) and (nghin<10) then delete(chuso,1,14);                     if tram<>0 then chuso:=chuso+doichu(tram);                     delete(chuso,1,1);                     chuso[1]:=upcase(chuso[1]);                     chuso:=chuso+` dong`;                     end;                     writeln(chuso);                     writeln;                     write(`Tiep nua khong? (Y/N)`);                     tiep:=readkey;                     until upcase(tiep)=`N`;                end.