#!/bin/bash

# Make temp files to store the sorted lists.
sorted_left_file=$(mktemp)
sorted_right_file=$(mktemp)

# Use awk to cut out a column, then sort by general numeric value, and store in a temp file.
left=$(awk '{print $1}' input.txt | sort -g --field-separator=\n -o $sorted_left_file)
right=$(awk '{print $2}' input.txt | sort -g --field-separator=\n -o $sorted_right_file)

# Print the filenames for debugging.
echo $sorted_left_file
echo $sorted_right_file

# Initialize the cumulative sum of absolute differences.
running_total=0

# Read from the two sorted files, and save the cumulative sum of absolute differences
# between corresponding lines.
while read left_val right_val; do
    difference=$((left_val - right_val))
    if [ $difference -lt 0 ]; then
        abs_value=$((difference * -1))
    else
        abs_value=$difference
    fi
    running_total=$((running_total + abs_value))

done <<< $(paste $sorted_left_file $sorted_right_file)

echo $running_total