G2.3 Given that $111111222222=c \times(c+1)$, find the value of $c$.
$\begin{array}{l} 111111222222=111111000000+222222 \\ =111111 \times 1000000+2 \times 111111 \\ =111111 \times 1000002 \\ 111111222222=111111 \times 3 \times 333334=333333 \times 333334 \\ c=333333\end{array}$