#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <algorithm>
//---------------------------
using namespace std;
//---------------------------
#define REP(i,n) for(int i = 0; i < (n); i++)
#define P(x) cout << (x) << "\n"
//---------------------------


int main(){
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);



  int n,k;cin >> n >> k;
  string s;cin >> s;
  vector<vector<int>> a;
  a.resize(n);
  REP(i,n){
    a[i].resize(2);
  }
  //a[i][0]<初期数値、a[i][1]<括弧状態0,1
  REP(i,n){
    a[i][0] = i;
    if (s[i] == '(') {
      a[i][1] = -1;
    }else{
      a[i][1] = 1;
    }
  }
  //削除
  int sum = 0;
  if (a[k-1][1] == -1) {
    for (int i = k-1; i < n; i++) {
      if (a[i][1] == -1) {
        sum--;
      }else{
        sum++;
      }
      if (sum == 0) {
        P(i+1);
        break;
      }
    }
  }else if (a[k-1][1] == 1) {
    for (int i = k-1; i >= 0; i--) {
      if (a[i][1] == -1) {
        sum--;
      }else{
        sum++;
      }
      if (sum == 0) {
        P(i+1);
        break;
      }
    }
  }

  return 0;
}