You probably are seeing that low CPU usage because the program uses just one processor. Other problem could be that your disk is very slow, and the processor is just waiting forever. Or another combination.
But, please notice that you attached a binary/compiled program, not the source code. If you don't have the source code of that, a full rewrite of your program is needed.
I can rewrite your program, to use all your computer resources, so you get the processing much faster.