#include <algorithm>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <ostream>
#include <queue>
#include <stack>
#include <string>
#include <vector>
#define INF 1000000000
#define rep(i,a,b) for (int i=(a);i<(b);i++)
#define rev(i,a,b) for (int i=(a)-1;i>=b;i--)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef queue<int> qi;
typedef queue< pair<int, int> > qpii;
typedef vector<int> vi;
typedef vector<int, int> vii;
typedef vector<string> vs;
typedef vector< pair<int, int> > vpii;
int dx[4] = { 0, 1, 0, -1 };
int dy[4] = { 1, 0, -1, 0 };

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

  int n,k;
  string s;
  cin >> n >> k >> s;

  int r=0, l=0;
  if(s[k-1] == '(') {
    l++;
    rep(i,k,n) {
      if(s[i] == '(') l++;
      else if(s[i] == ')') r++;
      if(l == r) {
        cout << i+1 << endl;
        return 0;
      }
    }
  } else if(s[k-1] == ')') {
    r++;
    rev(i,k-1,0) {
      if(s[i] == '(') l++;
      else if(s[i] == ')') r++;
      if(l == r) {
        cout << i+1 << endl;
        return 0;
      }
    }
  }

	return 0;
}