Tính được $234^{5}\equiv 12\pmod{23}$
$\rightarrow (234^{5})^{23}\equiv 12 \pmod{23}$
$234^{8} \equiv 9\pmod{23}$
$\rightarrow (234^{5})^{23}.234^{8}\equiv 16\pmod{23}$
$\rightarrow (234^{123})^{23}\equiv16\pmod{23}$
$234^{15}\equiv 3\pmod{23}$
$\rightarrow (234^{123})^{23}.234^{15}\equiv 2\pmod{23}$
$\rightarrow (234^{2844})^{23}\equiv 2\pmod{23}$
$234^{20}\equiv 13\pmod{23}$
$\rightarrow BT\equiv 3\pmod{23}$