#include <iostream>
#include <vector>
#include <set>
#include <algorithm>
#include <math.h>
#include <string.h>
#include <map>
#include <numeric>
#include <random>
#include <queue>
#include <deque>
#include <tuple>
#include <iomanip>
#include <iterator>
#include <functional>

using namespace std;
typedef long long ll;

const int INF = (1 << 30) - 1;
const ll INFLL= (1LL << 61) - 1;
const int MOD = 1000000007;
#define ALL(a) (a).begin(),(a).end()
#define rALL(a) (a).rbegin(),(a).rend()
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)

int main(){
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int N,K;
  string S;
  cin>>N>>K>>S;
  K--;
  vector<int>sum(N);
  sum[0]=1;
  REP(i,N-1){
    sum[i+1]=sum[i]+(S[i+1]=='(' ? 1 : -1);
  }
  int i=K,ans;
  if(S[K]=='('){
    while(true){
      if(sum[K]-1==sum[i] && S[i]==')'){
        ans=i+1;
        break;
      }
      i++;
    }
  }else{
    while(true){
      if(sum[K]+1==sum[i] && S[i]=='('){
        ans=i+1;
        break;
      }
      i--;
    }
  }
  cout<<ans<<endl;
}