Good character

Find the character that appears most often across all

possible substrings of a given string. If there are several write in java

characters with the same highest frequency, print the one

that is smallest in lexicographical order.

Function description Complete the solve$()$ function. The

function takes $2$ parameters and returns a character

denoting the answer to the question:

$N.$ Represents the length of the string

$S$ Represents the string

Input format for custom testing

Note: Use this input format if you are testing against custom

input or writing code in a language where we don't provide

boilerplate code.

The first line contains $T,$ which represents the number

of test cases.

For each test case:

The first line contains an integer $N.$

The second line contains the string $S.$