#include <stdio.h>

int main(void) {
	int n,k,c=1,i;
	char s[16384];
	scanf("%d%d%s",&n,&k,s);
	i = k - 1;
	if(s[i] == '('){
		while(1){
			i++;
			if(s[i] == ')'){c--;}else{c++;}
			if(!c){printf("%d\n",i+1);break;}
		}
	}
	else{
		while(1){
			i--;
			if(s[i] == '('){c--;}else{c++;}
			if(!c){printf("%d\n",i+1);break;}
		}
	}
	return 0;
}