#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ld=long double;
using vll=vector<ll>;
using pll=pair<ll,ll>;

using mint=modint;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

    ll N,K,d=1;
    string S;
    cin>>N>>K>>S;
    K--;
    if(S[K]=='('){
        for(int i=K+1;i<N;++i){
            if(S[i]=='(')d++;
            else d--;
            if(d==0){
                cout<<i+1<<endl;
                return 0;
            }
        }
    }else{
        for(int i=K-1;i>=0;--i){
            if(S[i]==')')d++;
            else d--;
            if(d==0){
                cout<<i+1<<endl;
                return 0;
            }
        }
    }
}