We've previously seen that, for example, $v(1$:$3)=0$ sets the first $3$ elements of a vector $v$ to $0.$ Alternately, $v(1$:$3)=\left[\begin{array}{ccc}1& 2& 3\end{array}\right]$ will set the first three elements to $1,2,$ and $3$ respectively. $v(2$:$5)=v(2$:$5)+3$ will add $3$ to the $2$nd through $5$ th elements. Based on this idea, write a function named problem. $1$ that takes in a vector $(1-$d array$)v$ as input, and returns a modified version of $v$ where every other element $(1$st$,3$rd$,5$ th$,$ etc.$)$ has been multiplied by $-1.$