• The secret word is a non-empty substring (A substring of S is de.ned as any consecutive sequence of characters belonging to S. For example, if S = abcd then a, abcd, ab, bc and bcd are some of the substrings of S but ac, aa, aabbccdd and dcba are not substrings of S) of S (possibly equal to S). 

• S starts with the secret word reversed. 

• colombia: if you take c and reverse it you get c. colombia starts with c, so this satis.es the two clues above. Furthermore, c is the longest word that satis.es the two clues so it must be the secret word. 

• abcdba: if you take ba and reverse it you get ab. abcdba starts with ab and there’s no longer substring that satis.es the two clues. 

• neversayeven: if you take even and reverse it you get neve. neversayeven starts with neve and there’s no longer substring that satis.es the two clues. 

• neveroddoreven: this case is a palindrome so if we reverse it we get the same string. neveroddoreven starts with neveroddoreven (since they are the same) and obviously there’s no longer substring that satis.es that, so this is the secret word. 

• listentothesilence: Notice the secret word might be somewhere in the middle of the big word.