Every formal verification tool guide:

“So this is how you can prove add_one”

“A̵͈̜̪͓͆n̸͔͉̦̐͋̌̾ḑ̶̬̥̬̐ ̵̺̲̬̆̀t̸̻̲̋͒͑͠h̵̤̤͎̮̎͝í̴̱͖ͅs̷͈̫̖̰̒̅ ̶̝̭͎̼̌̌i̷͖̱̰͋̾͛͝s̸̛͖͔̈̍ ̸̛̗̗̙̣h̴̟͒o̷̭̤̮͙̅w̴͈̭̄ͅ ̷͔̹̬͋̈́̒̾w̵̞̺͚̓͑͘ē̸̢̟͙̯ ̴͉̅̆̈́s̷̗̺̙̰̍̎̀ű̸͖͉̩̲̍̍͝m̵̢͍̲̉ḿ̸̱̍̄ȯ̵̹̙̗̥n̷̛̞̾̃̔ ̶̰̳̹̒̚t̴̖̺̉̒̎͝ḧ̸̨̯̥̘́͝e̸͚̲̻̘̾̓ ̷̼̮͙̘̑̋͑͌d̸̤̩̘̯̋̕̕͘ä̶͈͆͜r̶̢̛͈͖̻͐͌́k̴̬̑͋ ̶̛̻͈̐l̴͙̹̎̕o̷̤̔̔͘ŕ̶̥͒̇̕d̷͐ͅ”