#include<bits/stdc++.h>
//#include<atcoder/all>
//using namespace atcoder;
using namespace std;
using ll = long long;

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

	for(int i = k-1;i>=0;i--){
		if(i==k-1)continue;
		if(L[k-1]==L[i]){
			cout<<i+1<<endl;
			return 0;
		}
	}
}