#include <stdio.h>


int main(void) {
	char str[10010];
	int length,des;
    scanf ("%d %d",&length,&des);
    scanf ("%s",&str);

    int right,left;
    int vec;
    int answer;

	right=0;
	left=0;

    if (str[des-1] == '(') {
		for (int i = des-1; i < length; i++) {
			if ( str[i] == '('){
				right++ ;
			}else{
				left++ ;
			}
			if (right==left) {
				answer=i+1;
				break;
			}
		}
    } else {
		for (int i = des-1; i >= 0; i--) {
			if ( str[i] == '('){
				right++ ;
			}else{
				left++ ;
			}
			if (right==left) {
				answer=i+1;
				break;
			}
		}
	}
    printf("%d\n",answer);
}