You are given two strings \(s\) and \(t\) of length \(n\). You can select any two positions (can be from the same or different strings) and swap the characters at those two positions. You have to perform this operation exactly once in such a way that there exists maximum one position \(i\) \((1 \le i \le n)\) such that \(s_i !=t_i\). 
Determine whether it is possible to perform the operation such that the given condition holds or not.

Input format

• First line: A single integer \(T\) that denotes the number of test cases 
• For each test case:
  • First line: An integer \(n\) 
  • Next two lines: Strings \(s\) and \(t\) respectively

Output format

For each test case, print YES if a valid operation exists otherwise print NO in a single line.

Input constraints

• \(1 \le T \le 50\)
• \(1 \le n \le 10^3\)
• Both the strings \(s\) and \(t\) contain only lowercase English alphabets