n, k = [int(x) for x in input().split(' ')]
s = input()
inex_num = []
for index, num in enumerate(s):
    if num == '(':
        inex_num.append(index)
    
    elif num == ')':
        delete_index = inex_num.pop()
        if delete_index == k-1:
            print(index+1)
            break
        
        elif index == k-1:
            print(delete_index+1)
            break