#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, n) for (int i = (s); i < (int)(n); i++)
#define rep2(i, n, s) for (int i = (n - 1); i >= (s); i--)

template<class T> inline bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

ll p(ll a, ll m, ll mod = 0){
	if (!mod) {
	    if (m == 0) return 1;
    	if (m % 2 == 0) return p(a * a, m / 2);
	    return p(a * a, m / 2) * a;
	} else {
	    if (m == 0) return 1;
    	if (m % 2 == 0) return p(1L * a * a % mod, m / 2, mod);
    	return p(1L * a * a % mod, m / 2, mod) * a % mod;
	}
}

ll INF = 1000000000000000000;

// rep(i, 0, 4) => 上下左右, rep(i, 0, 8) => 斜めも含む
vector<int> dy = {-1, 0, 1, 0, -1, -1, 1, 1};
vector<int> dx = {0, 1, 0, -1, -1, 1, 1, -1};

int main() {
    int N, K;
    string S;
    cin >> N >> K >> S;
    int c = 0;
    if (S[K - 1] == '(') {
        rep(i, K, N) {
            if (S[i] == '(') c++;
            else c--;
            if (c < 0) {
                cout << i + 1 << endl;
                return 0;
            }
        }
    }
    else {
        rep2(i, K - 1, 0) {
            if (S[i] == ')') c++;
            else c--;
            if (c < 0) {
                cout << i + 1 << endl;
                return 0;
            }
        }
    }
}