Problem S2: Heavy-Light Composition

Problem Description

In a string containing only lowercase letters of the alphabet ("a" through "z"), we say a letter is heavy if it appears more than once in the string, and light otherwise.

We will be given a number of strings. For each string, we would like to determine whether the letters of the string alternate between light and heavy.

Input Specification

The first line of input will consist of two positive integers $T$ and $N$ , representing the number of strings and the length of each string.

The next $T$ lines each contain a sequence of $N$ lowercase letters of the alphabet.

The following table shows how the available $15$ marks are distributed:

Marks	Bounds on $T$	Bounds on $N$	Other Restrictions
$5$	$2 \le T \le 4$	$2 \le N \le 4$	Only the letters "a" and "b" will be used
$5$	$2 \le T \le 10$	$2 \le N \le 30$	None
$2$	$2 \le T \le 100$	$2 \le N \le 100$	Only the letter "a" will be heavy; all other letters are light
$3$	$2 \le T \le 10\ 000$	$2 \le N \le 100~~$	None

Output $T$ lines, where each line will be either T or F. If the $i$ -th input string does alternate between light and heavy letters, the $i$ -th line of output should be T; and otherwise, the $i$ -th line of output should be F.