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

if S[K-1] == "(":
    op = 0
    cl = 0
    for i in range(K, N):
        if S[i] == "(":
            op += 1
        else:
            cl += 1
        
        if cl - op == 1:
            print(i + 1)
            break
else:
    op = 0
    cl = 0
    for i in range(K-2, -1, -1):
        if S[i] == "(":
            op += 1
        else:
            cl += 1
        
        if op - cl == 1:
            print(i + 1)
            break