#include <iostream>

using namespace std;

int main()
{
	int N;    cin >> N;
	int K;    cin >> K;
	string S; cin >> S;
	
	int cnt = 0;
	int t = -1;
	int ret = 0;
	switch (S[K- 1])
	{
		case '(':
			for (int i = 0; i < N; i++)
			{
				switch (S[i])
				{
					case '(':
						cnt++;
						break;
					case ')':
						cnt--; 
						break;
				}
				
				if (t == cnt + 1) { cout << i + 1 << endl; break; } 
				if (i == K - 1) t = cnt;
			}
			break;
			
		case ')':
			for (int i = N - 1; i >= 0; i--)
			{
				switch (S[i])
				{
					case '(':
						cnt--;
						break;
					case ')':
						cnt++; 
						break;
				}
				
				if (t == cnt + 1) { cout << i + 1 << endl; break; } 
				if (i == K - 1) t = cnt;
			}
			break;
	}
	
	return 0;
}