N,K = map(int,input().split())
K -= 1
S = input()
A = []
c = 0
for s in S :
    if s == "(" :
        c += 1
        A.append(c)
    else :
        A.append(c)
        c -= 1

if S[K] == "(" :
    for i in range(K+1,N) :
        if A[K] == A[i] :
            print(i+1)
            break
else :
    for i in range(K-1,-1,-1) :
        if A[K] == A[i] :
            print(i+1)
            break