N, K = [int(i) for i in input().strip().split(" ")]
S = input()

stack = []

for idx,s in enumerate(S):
    if s == "(":
        stack.append([idx])
    else:
        tmp = stack.pop()
        tmp.append(idx)
        if K == (idx+1):
            print("%d"%(tmp[0]+1))
            break
        elif K == (tmp[0]+1):
            print("%d"%(idx+1))
            break