#!/usr/bin/env bash

tmp=$(mktemp)
while IFS= read -r line; do
    echo $line >> $tmp
done

last_line=$(cat $tmp | tail -n1)
cat $tmp | awk -F"," 'BEGIN{LAST=-1;skipped=0} {if(LAST!=$3){print $1","$2","$3;skipped=0}else{skipped=1} LAST=$3} END{if(skipped){print "'$last_line'"}}'
rm $tmp