#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;


int main(void) {
	cin.tie(0);
	ios::sync_with_stdio(false);

	int N, K;
	string S;
	cin >> N >> K;
	cin >> S;

	int pos = K - 1, level = 1, dir;
	char pare, other;
	if(S[pos] == '('){
		dir = 1;
		pare = '(';
		other = ')';
	}
	else{
		dir = -1;
		pare = ')';
		other = '(';
	}

	while(pos != 0 && pos != N){
		pos += dir;
		//cout << pos << " " << level << endl;

		if(S[pos] == pare){
			level++;
		}
		else{
			level--;
		}
		if(level == 0) break;
	}

	cout << pos + 1 << endl;

	return 0;
}