5x5 Crypto

We are given this set of numbers and characters:

1-3,4-4,2-1,3-1,1-5,1-1,4-2,3-3,{,4-4,2-3,4-5,3-2,1-2,4-3,_,4-5,3-5,}

And we are told that the encryption method takes a 5x5 grid with all letters of the alphabet in order. If we do a quick search, we will find Polybius Square, which is this one:

We can take every pair of i-j and match it to a letter finding the corresponding row-column cell. For instance, 1-1 is A and 5-5 is Z. After decrypting, we get CTFLEARN{THUMBS_UP}, so the flag will be: CTFlearn{THUMBS_UP}.