#include <iostream>
#include <cstring>
using namespace std;

int main(){
	char c[10001];
	int xxx[10001];
	int a,b;
	int x = 0;
	int i = 0;
	cin >> a>>b>>c;

	for(i=0; i<a ;i++){
		if(i==0) x++;
		if(c[i-1]=='(' && c[i] == '(') x++;
		else if(c[i-1]==')' && c[i] == ')') x--;
		xxx[i] = x;
	}
	if(c[b-1] == '(')  for(i=b;xxx[i]!=xxx[b-1];i++){}
	if(c[b-1] == ')')  for(i=b-2;xxx[i]!=xxx[b-1];i--){}
	cout << i+1 <<endl;

}