#include<iostream>
#include<algorithm>
#include<stack>
using namespace std;
using lint=int64_t;

int main()
{
	int N,K;
	string S;

	cin >> N >> K;
	cin >> S;
	K--;

	int ans=-1;
	stack<int> s;
	for(int i=0;i<S.size();i++)
	{
		if(S[i]=='(')
			s.push(i);
		else
		{
			if(i==K)
				ans=s.top();
			else
			{
				if(s.top()==K)
					ans=i;
				s.pop();
			}
		}
		if(ans!=-1)
			break;
	}

	cout << ans+1 << endl;
	return 0;
}