In $△XYZ$, $XY=XZ$. Points $A,B,$ and $C$ are on sides $\overline{XY},\overline{YZ},$ and $\overline{XZ}$, respectively, such that $\overline{AB}$ and $\overline{BC}$ are parallel to $\overline{XZ}$ and $\overline{XY}$, respectively. If the perimeter of parallelogram $XABC$ is $70$, what is the length of side $XY$?