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

count = 0

if S[M-1] == "(":
    for i in range(M, N):
        if S[i] == ")" and count == 0:
            print (i+1)
            break
        elif S[i] ==")":
            count -= 1
        else:
            count += 1
            
else:
    for i in range(M-2, -1, -1):
        if S[i] == "(" and count == 0:
            print (i+1)
            break
        elif S[i] =="(":
            count -= 1
        else:
            count += 1