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]

y = L[K-1]

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