# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N, K = getlist()
	cntSum = [0] * N
	cntSumRev = [0] * N
	S = input()
	cntSum[0] = 1
	cntSumRev[-1] = 1
	for i in range(1, N):
		if S[i] == "(":
			cntSum[i] = cntSum[i - 1] + 1
		else:
			cntSum[i] = cntSum[i - 1] - 1

	for i in range(N - 2, -1, -1):
		if S[i] == "(":
			cntSumRev[i] = cntSumRev[i + 1] - 1
		else:
			cntSumRev[i] = cntSumRev[i + 1] + 1
	# print(cntSum)

	K -= 1
	# print(val)
	if S[K] == "(":
		val = cntSum[K]
		for i in range(K + 1, N):
			if cntSum[i] == val - 1:
				print(i + 1)
				return
	else:
		val = cntSumRev[K]
		for i in range(K - 1, -1, -1):
			if cntSumRev[i] == val - 1:
				print(i + 1)
				return




if __name__ == '__main__':
	main()