1. Let the length of the sides of a triangle $\triangle ABC$ be integers with $A$ as the origin. $(2, -1)$ and $(3, 6)$ are points on the line $AB$ and $AC$ respectively (line $AB$ and $AC$ may be extended to contain these points), and lengths of exactly two sides are primes that differ by $50$. If $a$ is least possible length of the third side and $S$ is the least possible perimeter of the triangle, then $aS$ is equal to