#if !defined(__clang__) && defined(__GNUC__)
#include <bits/stdc++.h>
#else
#include <cstdlib>
#include <climits>
#include <iostream>
#include <cstdint>
#include <vector>
#include <string>
#include <complex>
#include <bitset>
#include <queue>
#include <deque>
#include <stack>
#include <utility>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <regex>
#endif //  !defined(__clang__) && defined(__GNUG__)
#if 0
#include <boost/lexical_cast.hpp>
#include <boost/algorithm/string.hpp>
#include <boost/multi_array.hpp>
#include <boost/optional.hpp>
#include <boost/math/common_factor_rt.hpp>
#endif

using namespace std;

int main()
{
    uint64_t N, K;
    std::cin >> N >> K;

    std::string S;
    std::cin >> S;

    if (S[K-1] == '(') {
        int64_t stack = 1;
        for (size_t i = K; i < N; ++i) {
            if (S[i] == ')') {
                stack--;
            }
            else {
                stack++;
            }
            if (stack == 0) {
                std::cout << i+1 << std::endl;
                return 0;
            }
        }
    }
    else {
        int64_t stack = 1;
        for (int64_t i = K-2; i >= 0; --i) {
            if (S[i] == '(') {
                stack--;
            }
            else {
                stack++;
            }
            if (stack == 0) {
                std::cout << i+1 << std::endl;
                return 0;
            }
        }
    }

    return 0;
}