const lines = require('fs')
  .readFileSync('/dev/stdin', 'utf-8')
  .trim().split('\n').values();

const [N, K] = lines.next().value.split(' ').map(x => Number(x));
const S = lines.next().value;

const bracket = [];
const position = [];
let ans;

bracket.push(S[0]);
position.push(0);

for (let i = 1; i < N; i++) {
  if (S[i] === ')' && bracket[bracket.length - 1] === '(') {
    bracket.pop();
    let p = position.pop();
    if (p === K - 1) {
      ans = i + 1;
      break;
    }
    if (i === K - 1) {
      ans = p + 1;
      break;
    }
  } else {
    bracket.push(S[i]);
    position.push(i);
  }
}

console.log(ans);