#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<string>
#include<vector>
#include<list>
#include<queue>
#include<utility>
#include <fstream>
#include<set>
#include<map>
#include<cctype>
#include<cmath>
#include<algorithm>
using namespace std;


#define RALL(x) (x).rbegin(),(x).rend()
#define ALL(x) (x).begin(),(x).end()
#define repp(i,n) for(int (i)=1;(i)<=(n);(i)++)
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rev(i,n) for(int (i)=(n-1);(i)>=0;(i)--)
#define clr(a) memset((a), 0 ,sizeof(a))

typedef pair<int,int> P;
typedef vector<pair<int,string> > pii;
typedef map<int,string> mdi;



int main(){
	int i,n,k,cnt=0;
	string s;
	cin >> n >> k >> s;
	k--;
	if(s[k]=='('){
		for(i=k;;i++){
			if(s[i]=='(')cnt++;
			else cnt--;
			if(cnt==0)break;
		}
	}
	else{
		for(i=k;;i--){
			if(s[i]=='(')cnt++;
			else cnt--;
			if(cnt==0)break;
		}
	}
	
	cout << i+1 << endl;
	return 0;
}