#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
#include <stack>
using namespace std;


int main(){
	int n, k;
	cin >> n >> k;
	k--;
	
	string s;
	cin >> s;

	int ans = -1;
	stack<int> x;
	for(int i=0; i<n; i++){
		if(s[i] == '('){
			x.push(i);
		}else{
			if(i==k){
				ans = x.top();
			}else if(x.top() == k){
				ans = i;
			}
			x.pop();
		}
	}

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