# import pypyjit
# pypyjit.set_param('max_unroll_recursion=-1')
from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

N,K = map(int,input().split())
S = list(input())[:-1]
L = deque()
R = deque()
Y = defaultdict(lambda:-1)
for i,s in enumerate(S):
    
    if s==')':
        j = L.pop()
        Y[j]=i
        Y[i]=j
    else:
        L.append(i)
        
print(Y[K-1]+1)