#include <stdio.h>

int main(){
	int len, val;
	scanf("%d %d",&len,&val);
	char str[len];
	char *p = str;
	
	for(int i = 0;i < len;i++){
		scanf("%c",&p[i]);
	}
	
	int count = 1;
	for(int i = val;i < len;i++){
		if(p[i] == '('){
			count++;
		}else{
			count--;
		}
		//printf("int：%d count：%d str：%c\n",i,count,p[i]);
		if(count == 0 && p[i] == ')'){
			printf("%d",i + 1);
			break;
		}
	}
}