n,k=map(int,raw_input().split())
s=raw_input()
t=[]
u=[]
for i in range(n):
	if s[i]=="(":
		t.append(i)
	else:
		j=t.pop()
		if i+1==k:
			print j+1
			exit()
		elif j+1==k:
			print i+1
			exit()