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

int main()
{
	int N, K;
	while( cin >> N >> K ){
		string S;
		cin >> S;
		int rank = 0;
		int memo = 0;
		for( int i = 0; i < N; ++i ){
			int p;
			if( S[ K - 1 ] == '(' ){
				p = i;
				if( p < K - 1 ) continue;
			}else{
				p = N - i - 1;
				if( p > K - 1 ) continue;
			}
			if( p == K - 1 ){
				memo = rank;
			}
			if( S[ p ] == '(' ) ++rank;
			if( S[ p ] == ')' ) --rank;
			if( memo == rank ){
				cout << p + 1 << endl;
				break;
			}
		}
	}

	return 0;
}