main () {
# Find the maximum number of leading digits in the filenames of working dir
max_digits="$(list_files | sed -e 's/[^0-9].*//' | awk '{ if(length > L) L=length } END { print L }')";
main () {
# Find the maximum number of leading digits in the filenames of working dir
max_digits="$(list_files | sed -e 's/[^0-9].*//' | awk '{ if(length > L) L=length } END { print L }')";