Given variables int n and double pi$,$ write a snippet of code that assigns to pi the approximation of $\backslash$pi resulting from adding the first n terms in the Gregory$-$Leibniz series:

$\backslash$pi

$=$

$4$

$\backslash$infty

$$

i

$=$

$0$

$($

$$

$1$

$)$

i

$2$

i

$+$

$1$

$=$

$4$

$($

$1$

$1$

$$

$1$

$3$

$+$

$1$

$5$

$$

$1$

$7$

$+$

$...$

$)$