#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#define p(s) cout<<(s)<<endl
#define REP(i,n,N) for(int i=n;i<N;i++)
#define RREP(i,n,N) for(int i=N-1;i>=n;i--)
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define F first
#define S second
typedef long long ll;
using namespace std;
const int inf = 1e9+7;

int N, K;
int idx[10010];
string s;
int ans;
int main() {
    cin>>N>>K>>s;
    REP(i, 0, s.size()){
        if(s[i]=='('){
            idx[i+1]=idx[i]+1;
        }else{
            idx[i+1]=idx[i]-1;
        }
    }
    if(s[K-1]=='('){
        REP(i,K+1,N){
            if(s[i-1]=='(') continue;
            if(idx[K] == idx[i]+1){
                ans=i;
                break;
            }
        }
    }else{
        RREP(i,1,K){
            if(s[i-1]==')') continue;
            if(idx[K] == idx[i]-1){
                ans=i;
                break;
            }
        }
    }
    p(ans);
    return 0;
}