#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <algorithm>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#define rep(i,l,n) for(lint i=l;i<n;i++)
#define rer(i,l,n) for(lint i=l;i<=n;i++)
#define all(a) a.begin(),a.end()
#define o(a) cout<<a<<endl
#define pb(a) push_back(a)
#define mk(a,b) make_pair(a,b)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef vector<int> vi;
typedef vector<lint> vli;
typedef vector<vi> vvi;
typedef pair<int,int> pii;

int main(){
	int n,k;
	string s;
	cin>>n>>k>>s;
	k--;
	int f=0,key=0,ans;
	vi d(n);
	rep(i,0,n){
		if(s[i]=='('){
			f++;
			d[i]=f;
		}else{
			d[i]=f;
			f--;
		}
		if(i==k) key=d[i];
	}
	if(s[k]=='('){
		rep(i,k+1,n){
			if(d[i]==key){
				ans=i+1;
				break;
			}
		}
	}else{
		for(int i=k-1;i>=0;i--){
			if(d[i]==key){
				ans=i+1;
				break;
			}
		}
	}
	o(ans);
}