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

x = 1
l = []
for i in range(n):
    if s[i] == '(':
        l.append(x)
        x += 1
        
    elif s[i] == ')':
        x -= 1
        l.append(x)

y = l[k-1]

if s[k-1] == '(':
    z = l[k:].index(y) + 1
    print(z + k)
else:
    z = l[:k-1][::-1].index(y) + 1
    print(k - z)