If the square of the shortest distance between the lines
$$ \frac{x-2}{1} = \frac{y-1}{2} = \frac{z+3}{-3} \quad \text{and} \quad \frac{x+1}{2} = \frac{y+3}{4} = \frac{z+5}{-5}, $$
is $ \frac{m}{n} $, where $m, n$ are coprime numbers, then $m+n$ is equal to: