#include <algorithm>
#include <array>
#include <cstdio>
#include <iostream>
#include <numeric>
#include <optional>
#include <vector>

using namespace std;

int main() {
    int32_t n, k;
    string s;
    cin >> n >> k >> s;
    --k;
    optional<int32_t> ans;
    if (s[k] == '(') {
        int32_t cnt = 0;
        for (auto i = k; i < n; ++i) {
            if (s[i] == '(')
                ++cnt;
            else if (cnt == 1) {
                ans = i;
                break;
            } else
                --cnt;
        }
    } else {
        int32_t cnt = 0;
        for (auto i = k; i >= 0; --i) {
            if (s[i] == ')')
                ++cnt;
            else if (cnt == 1) {
                ans = i;
                break;
            } else
                --cnt;
        }
    }
    cout << ans.value() + 1 << endl;
    return 0;
}