N, M = map(int, input().split())
S = input()
d = c = a = 1
if S[M-1] == ")" : d = -1
while 1:
    if S[M-1 + c * d] == S[M-1]:
        a += 1
    else:
        a -= 1
    if a == 0 : break
    c += 1
print(M + c * d)