import sys
N,K = map(int, raw_input().split())
pare = raw_input()
stack = []
for i in range(N):
    if (pare[i] == '('):
        stack.append(["(", i + 1])
    else:
        pos = stack.pop()
        if ((i + 1) == K):
            print pos[1]
            sys.exit(0)
        if (pos[1] == K):
            print i + 1
            sys.exit(0)