#include <stdio.h>

int main(){

	int N, K;
	scanf("%d %d", &N, &K);

	char S[N];
	scanf("%s", S);

	int i, d, count;
	d = count = S[K - 1] == '(' ? 1 : -1;

	for(i = K - 1 + d; -1 < i && i < N; i += d){
		count += S[i] == '(' ? 1 : -1;
		if(count == 0) break;
	}

	printf("%d", i + 1);

	return 0;
}