Câu 1:
uses crt;
var s:string;
i,count:word;
begin
clrscr;
readln(s);
for i:=1 to length(s) do
if s[i]='a' then inc(count);
write(count);
readln;
end.
Câu 2:
uses crt;
var s:string;
begin
clrscr;
readln(s);
write(upcase(s));
readln;
end.
Câu 3:
uses crt;
var s1,s2:string;
begin
clrscr;
readln(s1);
readln(s2);
insert(s1,s2,1);
write(s2);
readln;
end.