In the 5 by 5 matrix below, the minimal path sum from the top left to the bottom right, 
by only moving to the right and down, is indicated in bold red and is equal to 2427.

~~~
131 673 234 103 018
201 096 342 965 150
630 803 746 422 111
537 699 497 121 956
805 732 524 037 331
~~~

Find the minimal path sum, in matrix.txt (right click and "Save Link/Target As..."), 
a 31K text file containing a 80 by 80 matrix, 
from the top left to the bottom right by only moving right and down.