#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<ll> vll;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<vector<ll>> vvll;
const ll inf = 1e16;
const ll md = 1000000007;

int main() {
  int n,k;
  string s;
  cin>>n>>k>>s;
  k--;
  int cnt=0;
  if(s[k]=='('){
    for(int i=k+1;i<n;i++){
      if(s[i]=='(') cnt++;
      else{
        if(cnt) cnt--;
        else{
          cout<<i+1<<endl;
          return 0;
        }
      }
    }
  }
  else{
    for(int i=k-1;k>=0;i--){
      if(s[i]==')') cnt++;
      else{
        if(cnt) cnt--;
        else{
          cout<<i+1<<endl;
          return 0;
        }
      }
    }
  }
  return 0;
}