79. Calculate the sum

$$
1^{2}-2^{2}+3^{2}-4^{2}+\ldots+99^{2}-100^{2}+101^{2}
$$
$$
\begin{gathered}
1^{2}-2^{2}+3^{2}-4^{2}+\ldots+101^{2}= \\
=1+(101^{2}-100^{2})+(99^{2}-98^{2})+\ldots+(3^{2}-2^{2})= \\
=201+197+\ldots+9+5+1= \\
=\frac{1}{2}(201+1) \cdot 51=101 \cdot 51=5151
\end{gathered}
$$

Answer: 5151.