#include<bits/stdc++.h>
#define rep(i,a,n) for (int i = a;i < n;i++)
using namespace std;

int main() {
    char check;
    int n,k,ans; cin >> n >> k;
    vector<int> bracket(n+1,0);
    rep(i,0,n){
        char input; cin >> input;
        if(i == k-1) check = input;
        switch(input){
            case '(': ++bracket[i]; break;
            case ')': --bracket[i+1]; break;
        }
    }
    rep(i,1,n+1){
        bracket[i] += bracket[i-1];
    }
    if(check=='('){
        ans=k+1;
        while(bracket[k-1]!=bracket[ans-1]) ++ans;
    }else{
        ans=k-1;
        while(bracket[k-1]!=bracket[ans-1]) --ans;
    }
    cout << ans << "\n";

    return 0;
}