#include <stdio.h>

int main(void) {

	int count, number, kazu = 0;
	char kakko[256];
	int i;
	scanf("%d %d\n", &count, &number);

	for (i = 0; i < count; i++) {
		scanf("%c", &kakko[i]);

	}
	for (i = number-1; i < 10000; i++) {
		if(i == count){
			i = -1;
		}else {
			if(kakko[i] == '('){
				kazu++;
			}else{
				kazu--;
			}
			if(kazu == 0){
				printf("%d",i+1);
				break;
			}
		}
	}

	return 0;
}