#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <algorithm>
#include <numeric>
#include <functional>
#include <set>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cctype>
#include <climits>

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define EXIST(v, n) (std::find(v.begin(), v.end(), 1) != v.end())

using namespace std;

int main(int argc, char *argv[]) {
	int N, K, i, j = 0;
	string S;
	cin >> N >> K; K--;
	cin >> S;
	for (i = K; ;  S[K] == '(' ? ++i : --i) {
		if (S[i] == ')') { j++; }
		else { j--; }
		if (j == 0) { break; }
	}
	cout << i + 1 << endl;
}