Heh at first i thought 'wait how did they get all 512bits in a collision!?'
Then i realized the program just calculates it's own hash and prints it. Simple as that. It'd be super interesting if the program had the hash as a string internally and printed that out but that's (within the realm of breaking cryptography) impossible to pull off.
https://www.ioccc.org/years.html#2019_diels-grabsch2