{$H+}
var s:string;
i:longint;
f:text;
begin
writeln('nhap sau ki tu can xu li');
readln(s);
for i:=1 to lenght(s) do
if not(s[i] in ['A'..'Z']) and not(s[i] in ['0'..'9']) then
then delete(s,i,1);
assign(f,'dulieu.txt');reset(f);
write(f,'chuoi sau khi xu li:',s);
close(f);
end.