#include <bits/stdc++.h>
using namespace std;

int main()
{
	int n, k;
	string s;
	cin >> n >> k >> s;
	k--;
	
	deque<pair<char, int>> dq;
	for(int i = 0; i < n; i++)
	{
		if(dq.empty()) dq.push_back({s[i], i});
		else
		{
			if(dq.back().first == '(' && s[i] == ')')
			{
				if(dq.back().second == k)
				{
					cout << i + 1 << endl;
					return 0;
				}
				if(i == k)
				{
					cout << dq.back().second + 1 << endl;
					return 0;
				}
				dq.pop_back();
			}
			else dq.push_back({s[i], i});
		}
	}
	return 0;
}