#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<vector>
#include<cmath>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<numeric>
#include<functional>
#include<complex>

using namespace std;
#define BET(a,b,c) ((a)<=(b)&&(b)<(c))
#define FOR(i,n) for(int i=0,i##_end=(int(n));i<i##_end;i++)
#define SZ(x) (int)(x.size())
#define ALL(x) (x).begin(),(x).end()
#define MP make_pair
#define FOR_EACH(it,v) for(__typeof(v.begin()) it=v.begin(),it_end=v.end() ; it != it_end ; it++)
typedef vector<int> VI;
typedef vector<VI> VVI;

int main()
{
    int N,K;
    cin>>N>>K;
    string S;
    cin>>S;
    K--;
    if(S[K] == '('){
        int dep = 1;
        while(dep > 0){
            ++K;
            if(S[K] == '(') dep++; else dep--;
        }
    }else {
        int dep = 1;
        while(dep > 0){
            --K;
            if(S[K] == ')') dep++; else dep--;
        }
    }
    cout<<K+1<<endl;
    return 0;
}