#!/usr/bin/env python
# -*- coding: utf-8 -*-
if __name__ == '__main__':
    
    n , k = [int(i) for i in input().split()]
    s = input()
    
    stack = []
    result = 0
    for i in range(n):
        
        if s[i] == "(":
            stack.append(i + 1)
        else:
            kakko_s = stack.pop()
            kakko_e = i + 1
            
            d = {kakko_s: kakko_e, kakko_e: kakko_s}
            if k in d:
                result = d[k]
            
    print(result)