One of the most indispensable things about a great text editor for programming is the ability to quickly jump between matching parentheses. If you have a line like,

    if (f(a) >= b(c, d(e*(f-g))))

it very convenient to place your cursor at, say, the second to last closing parenthesis, and have the editor show you where is the matching opening parenthesis. (In this example, it is the one just after b.)

For this problem, you should write a function that takes a string s like 'if (f(a) >= b(c, d(e*f(-g))))' and an integer n representing a character position within the string. Your function should return the index of the matching parenthesis.

For example:

    >> s = 'if (f(a) >= b(c, d(e*f(-g))))';

    >> find_matching_paren(s, 4)

    ans =

        29

    >> find_matching_paren(s, 6)

    ans =

         8

    >> find_matching_paren(s, 27)

    ans =

        19

You can assume that n will always be the position of either an open or closing parenthesis.

You can assume the string will always have balanced parentheses.