N, K = map(int, input().split())
S = input()

L = []
x = 1
for s in S:
    if s == '(':
        L += [x]
        x += 1
    else:
        x -= 1
        L += [x]

if S[K-1] == ')':
    print(L[:K-1].index(L[K-1]) + 1)
else:
    print(K + L[K:].index(L[K-1]) + 1)