#include <stdio.h>
#include <stdlib.h>

int main(void)
{
  int N, K, i;
  char* s;
  int right, left;
  
  scanf("%d %d", &N, &K);
  s = (char*)malloc(N * sizeof(char));
  scanf("%s", s);
  right = left = 0;

  if(s[K-1] == '(') {
    for (i = K; i < N; i++) {
      if (s[i] == '(')
	right++;
      else {
	if (right == 0) {
	  printf("%d\n", i+1);
	  break;
	}
	else
	  right--;
      }
    }
  }
  else {
    for (i = K-2; i >= 0; i--) {
      if (s[i] == ')')
	left++;
      else {
	if (left == 0) {
	  printf("%d\n", i+1);
	  break;
	}
	else
	  left--;
      }
    }
  }
  
  return 0;
}