The numbers... what do they mean?
We get a bit of an image:
The {} suggest that this is some sort of transposition, where letters are replaced with numbers while other characters are left the same. Since all the numbers are in the range 0-25, it makes logical sense that each number is really the position of the letter in the alphabet. We can make a simple decryption script based off this assumption:
We get QJDPDUG{UIFOVNCFSTNBTPO}. As we assume it starts with PICOCTF, we can see that we are actually one index off - which makes sense, as strings are zero-indexed in Python, so we just need to use n-1 and we get the flag: