#include <stdio.h>

char kakko[10010];
int N,K;
int main(void) {
    scanf ("%d %d",&N,&K);
    scanf ("%s",&kakko);

    int right,left;
    int vec;
    int answer;

	right=0;
	left=0;

    if (kakko[K-1] == '(') {
		for (int i = K-1; i < N; i++) {
		    if ( kakko[i] == '(')
		        right++ ;
		    else
		        left++ ;
		    
		    if (right==left) {
		        answer=i+1;
		        break;
			}
		}

    } else {
	  for (int i = K-1; i >= 0; i--) {
	        if ( kakko[i] == '(')
	            right++ ;
	        else
	            left++ ;
	        
	        if (right==left) {
	            answer=i+1;
	            break;
			}
    }

    }

    printf("%d\n",answer);

    return 0;
}