#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
using ll=long long;
using Graph=vector<vector<int>>;
#define MAX 1000000
#define MOD 1000000007
//#define MOD 998244353
#define INF 1000000000
//#define INF 1000000000000000000

int main(){
  int N,K;
  string S;
  cin>>N>>K>>S;
  int i=K-1;
  int x=0;
  if(S[i]=='('){
    while(true){
      if(S[i]=='('){
        x++;
      }else{
        x--;
      }
      if(x==0){
        cout<<i+1<<endl;
        return 0;
      }
      i++;
    }
  }else{
    while(true){
      if(S[i]==')'){
        x++;
      }else{
        x--;
      }
      if(x==0){
        cout<<i+1<<endl;
        return 0;
      }
      i--;
    }
  }
}