n, k = map(int, input().split())
s = list(input())

l = [1]
d = 1
for i in range(1, len(s)):
    if s[i-1] == '(' and s[i] == '(':
        d += 1
        l.append(d)
    elif s[i-1] == ')' and s[i] == ')':
        d -= 1
        l.append(d)
    else:
        l.append(d)

x = l[k-1]

y = [i+1 for i, j in enumerate(l) if j == x]
print(y[-1])