#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<map>
#include<set>
#include<cstdio>
#include<cmath>
#include<numeric>
#include<queue>
#include<stack>
#include<cstring>
#include<limits>
#include<functional>
#include<unordered_set>
#include<iomanip>
#include<cassert>
#include<regex>
#define rep(i,a) for(int i=(int)0;i<(int)a;++i)
#define pb push_back
#define eb emplace_back
using ll=long long;
constexpr ll mod = 1e9 + 7;
constexpr ll INF = 1LL << 50;
 
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
using namespace std;

void solve(){
    int n,k;
    cin>>n>>k;
    string s;
    cin>>s;
    vector<int>imos(n+5),sum(n+5);
    rep(i,n){
        if(s[i]=='('){
            imos[i]++;
        }
        else imos[i+1]--;
    }
    rep(i,n)sum[i+1]=sum[i]+imos[i];
    set<int>ss;
    rep(i,n){
        if(sum[i+1]==sum[k]){
            ss.insert(i+1);
        }
    }
    if(s[k-1]==')')cout<<*prev(ss.find(k))<<"\n";
    else cout<<*next(ss.find(k))<<"\n";
}
 
int main(){
	ios::sync_with_stdio(false);
    cin.tie(0);
	cout<<fixed<<setprecision(15);
	solve();
	return 0;
}