n,k = map(int,input().split())
s = input()
cnt = 0
if s[k-1]==")":
    for i in range(n):
        if s[k-1-i]==")":
            cnt += 1
        else:
            cnt -= 1
        if cnt == 0:
            break
    print(k-i)
else:
    for i in range(n):
        if s[k-1+i]=="(":
            cnt += 1
        else:
            cnt -= 1
        if cnt == 0:
            break
    print(k+i)