Training Site

# Twilight Sparkle's Magic Spells

Input: Standard Input (stdin)
Output: Standard Output (stdout)
Memory limit: 100 megabytes
Time limit: 1.0 seconds

Twilight Sparkle is researching some magic spells. A spell is a non-empty finite sequence of Apples, Bananas, or Ciwifruit.

Spells can be safe or unsafe. An unsafe spell contains one or more of the following patterns:

Pattern Name
AAAAA Appleboom
ABBA Stockholm Syndrome
ABCABC Double Rainbow

Help Twilight determine whether a spell is safe or unsafe.

## Input

The first line of input will contain a single integer, $0 \lt N \le 100$, representing the length of the spell.

The next line will contain a string of $N$ letters, each either A, B, or C. This is the spell itself.

## Output

Output SAFE if the spell is safe; otherwise UNSAFE.

## Explanations

• BAAAAAB is unsafe, as it contains an Appleboom.
• AAAACA is safe. While it has five Apples, the Ciwifruit in between means that it can't form an Appleboom.
• ABBABBA is unsafe, as it contains two (overlapping) Stockholm Syndromes.
• ABBAAAAA is also unsafe, as it contains both a Stockholm and an Appleboom. They don't cancel out!
• CBACBA is safe. It has the same fruit as a Double Rainbow, but the fruit are in the wrong order.
• ### Sample Input 1

7
BAAAAAB


### Sample Output 1

UNSAFE

• ### Sample Input 2

6
AAAACA


### Sample Output 2

SAFE