#include <bits/stdc++.h>
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define RREP(i,a,b) for(int i=(a);i>=(b);i--)
#define pq priority_queue
#define P pair<int,int>
#define P2 pair<int,P>
#define P3 pair<int,P2>
typedef long long ll; typedef long double ld;
using namespace std;
const int INF=1e9, MOD=1e9+7, around[]={0,1,1,-1,-1,0,-1,1,0,0};
const ll LINF=1e18;
const ld PI=abs(acos(-1));
int n,k;
string s;
stack<pair<char,int>> st;

int main(){
	cin >> n >> k >> s; k--;
	
	REP(i,0,n){
		if(st.size() and st.top().first=='(' and s[i]==')'){
			if(st.top().second==k){cout << i+1 << endl; break;}
			else if(i==k){cout << st.top().second+1 << endl; break;}
			else st.pop();
		}else st.push(make_pair(s[i],i));
	}
	
	return 0;
}