#include <iostream>
#include <vector>
#include <algorithm>
#include <math.h>

#define ALL(x) (x).begin(),(x).end()
#define REP(i,n) for(int i = 0;i < (n);i++)

using namespace std;

int main(){
    int n,k;
    string s;
    cin >> n >> k >> s;
    int count = 0,i;
    for(i = k-1;;i += s[k-1] == '(' ? 1 : -1){
        if(s[i] == '(')count++;
        else if(s[i] == ')')count--;
        
        if(count == 0)break;
    }
    cout << i + 1 << endl;
    return 0;
}