#include <stdio.h>

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

    int right,left;
    char vec;
    int answer;

    int start=kakko[K] ;  
    if (kakko[K] == '(') {
        vec=1 ;
        right=1 ;
    } else {
        vec=-1 ;
        left=1 ;
    }

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

    }

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

    return 0;
}