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“It's not that I'm so smart, it's just that I stay with problems longer .”

-- Albert Einstein

-- Albert Einstein

\begin{bmatrix} 1 & 0 & \ldots & 0 \\
0 & 1 & 0 & \vdots \\
\vdots & 0 & \ddots & 0\\
0 & \ldots & 0 & 1_{n}
\end{bmatrix}