Use egrep (or grep -E) to find all words in the file /usr/red/words.txt that contain the same 3-letter sequence at least three times. For example, one such word matched by the correct regular expression is cha-cha-cha. It contains the 3-letter sequence cha three times. Other example output can be man-man-man oh-oh-oh , please make sure to match any 3 letters that are in sequence.