let input = require('fs').readFileSync('/dev/stdin', 'utf8')
let [N, K, S] = input.split(/\s/);
K = Number(K);
S = S.replace('\n', '');
let a = str => str == '(' ? 1 : -1;
let t = c = a(S[K - 1])
let e = K - 1 + t;
for (;;) {
  c += a(S[e]);
  e += t;
  if (c == 0) break;
}
console.log(1 + e - t);