#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(n);++i)
#define ALL(A) A.begin(), A.end()

using namespace std;

typedef long long ll;
typedef pair<int, int> P;

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	int N, K; cin >> N >> K;
	string S; cin >> S;

	stack<P> st;
	vector<P> par; par.clear();
	rep (i, N){
		if (S[i] == '('){
			st.push(P(i,-1));
		}else{
			P curr = st.top(); st.pop();
			curr.second = i;
			par.push_back(curr);
		} // end if
	} // end rep

	int res = 0;
	rep (i, par.size()){
		if (K - 1 == par[i].first){
			res = par[i].second + 1;
			break;
		} // end if
		if (K - 1 == par[i].second){
			res = par[i].first + 1;
			break;
		} // end if
	} // end rep
	cout << res << endl;

	return 0;
}