#include <iostream>
#include <iomanip>
using namespace std;
 
int main(){
    int N, K;
    string S;
    cin >> N >> K >> S;
    int if_open_bracket = -1;
    if(S[K - 1] == '('){
        if_open_bracket = 1;
    }
    int start_bracket_equal = 0;
    for(int i = K - 1; i < N; i += if_open_bracket){
        if(S[i] == '(' ^ if_open_bracket == 1){
            start_bracket_equal++;
        }else{
            start_bracket_equal--;
        }
        if(!start_bracket_equal){
            cout << i + 1 << endl;
            return 0;
        }
    }
}