program bt;
uses crt;
var a: string;
i: byte;
x: char;
begin
clrscr;
write('Nhap xau a:'); readln(a);
write('Nhap ki tu x:'); readln(x);
for i := 1 to length(a) do if a[i] = x then a[i] := upcase(a[i]);
write('Xau moi la:');
for i := 1 to length(a) do write(a[i]);
readln
end.
Xin câu trả lời hay nhất ạ :3