import sys
input=lambda:sys.stdin.readline().rstrip()
N,K=map(int,input().split())
S=input()
K-=1
pointer=K
count=1
while 1:
	pointer+=[1,-1][S[K]==')']
	count+=[1,-1][S[K]!=S[pointer]]
	if count==0:
		print(pointer+1)
		sys.exit()