## PLNDROME - Palindrome Or Not

```It's English class now. So John is bored as usual. To get over his boredom he is doing a very strange thing. He writes an arbitrary string on his notebook and then keeps changing a single character of the string every time and tries to find out  if the string has become a palindrome.
As John is very smart this task is very simple for him.
But how simple is it for you ? Can you be as smart as the great John?
You'll have to write a code that solves the similar problem and hopefully as fast as John.

INPUT:
First line of the input will be an integer T (T<=15) denoting number of test cases.
Each test case starts with an integer N (1<=N<=100000) denoting the length of the string.
Next line will contain the string consisting of only small letters of English alphabet (a,b,c,...,x,y,z).
Then there will be another integer M (1<=M<=10000) denoting number of queries.
Each query will be in the form:  i x
where i will be an integer (1<=i<=N) and x will be a character. (a<= x<=z)
and it will mean that the i-th character of the string has been changed to x.

OUTPUT:
First you will have to print the test case number.
Then for each query in  the test case you will have to print "YES" if the given string has become a plaindrome. Otherwise print  "NO". (without the quotes )
See sample input/output and expalination for details.

Sample   Input

Sample   output

1
11
6
6 z
1 a
11 b
5 z
1 b
7 z

Case 1:
YES
NO
NO
NO
NO
YES

Explaination:
which is a palindrome

which is  NOT a palindrome

which is  NOT a palindrome