uses crt;
var s1, s2 : string; i : byte;
begin
clrscr;
write('Nhap xau s1 = '); readln(s1);
s2 := '';
for i := 1 to length(s1) do
begin
if s1[i] in ['A' .. 'Z'] then s2 := s2 + s1[i];
if s1[i] in ['a' .. 'z'] then s2 := s2 + s1[i];
end;
write('Xau s2 = ', s2);
readln
end.