[Reverse] DSYM - Stuck on challenge

Hello everybody
I’m new to RevEng and I’m stuck with this challenge.
I found the string “You almost got me: D here is small pri” … with IDAPro, radare2 and Ghidra. some more information me the Ghidra date.
I also understood the “while” block but I just can’t go on.
with Ida I tried to do a Debug step by step but I couldn’t find the way to get to that SubRoutine.
someone can give me a clue … even in PM