n,m = map(int,input().split())
s = input()
A = []
for i,t in enumerate(s):
    i += 1
    if '('==t:
        A.append(i)
    elif ')'==t:
        a = A.pop()
        if i == m:
            ans = a 
        if a == m:
            ans = i
print(ans)