#include <iostream>
#include <string>

int main(void)
{
	int N, K;
	
	std::cin >> N >> K;

	std::string S;

	int a[N];
	
	std::cin >> S;
	
	//(()(()))
	//(21(()))
	//(21(45))
	//(216543)
	//72165430
	
	int beg = (int)S[0];
	int end = (int)S[N - 1];
	
	for(int i = 0; i < N; i++)
	{
		if((int)S[i] == beg)
		{
			a[i] = -1; //(
		}
		else
		{
			a[i] = -2; //)
		}
	}
	
	for(int i = 0; i < N / 2; i ++)
	{
		for(int j = 0; j < N; j ++)
		{
			if(a[j] == -2)
			{
				for(int k = j - 1; k >= 0; k --)
				{
					if(a[k] == -1)
					{
						a[k] = j;
						a[j] = k;
						break;
					}
				}
			}
		}
	}
	
	std::cout << (a[K - 1] + 1) <<std::endl;

	return 0;
}