program CardTest;
 
 uses
   Dialogs,
   SysUtils;
 
 {$R *.RES}
 
 const
   CardType : array [0..4] of string = ('Invalid', 'Amex', 'Visa', 'Mastercard',
     'Discover' );
 
 function Vc(C: string) : Integer;
 var
   Card  : string[21];
   VCard : array [0..21] of Byte absolute Card;
   XCard : Integer;
   Cstr  : string[21];
   y,
   x     : Integer;
 begin
   Cstr := ''; 
   FillChar(VCard, 22, #0); 
   Card := C; 
   for x := 1 to 20 do 
     if (VCard[x] in [48..57]) then 
       Cstr := Cstr+Chr(VCard[x]); 
   Card := ''; 
   Card := Cstr; 
   XCard := 0; 
   if not odd(Length(Card)) then 
     for x := (Length(Card)-1) downto 1 do 
     begin 
       if odd(x) then 
         y := ((VCard[x]-48)*2) 
       else 
         y := (VCard[x]-48); 
       if (y>=10) then 
         y := ((y-10)+1); 
       XCard := (XCard+y) 
     end 
   else 
     for x := (Length(Card)-1) downto 1 do 
     begin 
       if odd(x) then 
         y := (VCard[x]-48) 
       else 
         y := ((VCard[x]-48)*2); 
       if (y>=10) then 
         y := ((y-10)+1); 
       XCard := (XCard+y) 
     end; 
     x := (10-(XCard mod 10)); 
   if (x=10) then 
     x := 0; 
   if (x=(VCard[Length(Card)]-48)) then 
     Vc := Ord(Cstr[1])-Ord('2') 
   else 
     Vc := 0 
 end; 
 
 begin
   ShowMessage(CardType[Vc('4479750100222862')]);
 end.