#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <list>
#include <map>
#include <queue>
#include <iterator>
#include <cmath>
#include <iomanip>
using namespace std;

using ull = unsigned long long;
using ll = long long;

int main()
{
    int n,k;
    cin >> n >> k;
    string s;
    cin >> s;

    int count = 0;

    int result = 0;

    if(s.at(k-1) == '(')
    {
        for(int i = k-1; i < n; ++i)
        {
            if(s.at(i) == '(')  ++count;
            else --count;

            if(count == 0)
            {
                result = i+1;
            }
        }
    }
    else
    {

        for(int i = k-1; i >= 0; --i)
        {
            if(s.at(i) == ')')  ++count;
            else --count;

            if(count == 0)
            {
                result = i+1;
            }
        }
    }

    cout << result << endl;

}