#include <stdio.h>
#include <stdlib.h>

int main(void)
{
	short n,k,i,ans;
	char *c;
	scanf("%hd %hd",&n,&k);
	c = (char *)malloc(sizeof(char) * n);
	scanf("%s",c);

	if (c[k-1] == '(') {
		for (i=0;k-1<n;k++) {
			if      (c[k-1] == '(') i++;
			else if (c[k-1] == ')') i--;

			if (i<=0) break;
		}
	} else if (c[k-1] == ')') {
		for (;k-1>=0;k--) {
			if      (c[k-1] == ')') i++;
			else if (c[k-1] == '(') i--;

			if (i<=0) break;
		}
	}

	printf("%hd\n",k);

	return 0;
}