uses crt;
 var a,b,c,d :  integer ;
  s ,a1,b1,c1,d1,kt: string ;
   i : byte ;
   begin
    clrscr;
    write('Nhap so a: ');
     readln(a);
    write('Nhap so b: ');
     readln(b);
    write('Nhap so c: ');
     readln(c);
    write('Nhap so d: ');
     readln(d);
    str(a,a1);str(b,b1);str(c,c1);str(d,d1);
    s := concat(a1,b1,c1,d1);
    for i:=length(s) downto 1 do 
     kt := kt + s[i];
 if kt=s then writeln(a,b,c,d,' la 4 chu so thuoc so doi xung')
  else writeln(a,b,c,d,' khong la 4 chu so thuoc so doi xung');
    end.

uses crt;

var a, b, c, d : byte;

begin

    clrscr;

    readln(a, b, c, d);

    if (a = d) and (b = c) then

        write('Doi xung')

    else write('Khong doi xung');

    readln

end.