heart25.txt
greeting57.txt    Maia Ginsburg
jerry47.txt       Alex Ander (based on Japanese nonogram)
sedgewick60.txt   Alex Ander
michael61.txt     Alex Ander
wayne98.txt       Alex Ander
java60.txt        Ilyas Bambrik
eagle25.txt	  Sébastien Cabrit
princeton96.txt	  Sébastien Cabrit

To convert from 0-based indexing to 1-based indexing:
awk '{ if (NR > 1) { $1++; $2++; printf "%2d %2d\n", $1, $2 } else printf "%d\n", $1 }' snake13.txt

To convert from 1-based indexing to 0-based indexing:
awk '{ if (NR > 1) { $1--; $2--; printf "%2d %2d\n", $1, $2 } else printf "%d\n", $1 }' snake13.txt
