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

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