n, k = map(int,raw_input().split())
line = raw_input()

if line[k-1] == "(":
	a = 1
else:
	a = -1
	
b = 0
c = 0
while True:
	b += a
	if line[k+b-1] != line[k-1]:
		if c == 0:
			ans = k+b
			break
		else:
			c -= 1
	else:
		c += 1
print ans