uses crt;
var s1, s2 : string; i : byte;
begin
clrscr;
write('Nhap xau s1 : '); readln(s1);
s2 := ''; i := 1;
while i <= 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];
i := i + 1;
end;
write('Xau s2 : ', s2);
readln
end.