<?php
list($length, $point) = explode(" ",trim(fgets(STDIN)));
$tree = 0;
$str = trim(fgets(STDIN));
if ( $str[$point-1] == '(' ) {
  $other = strlen(substr($str,0,$point-1));
  $str = substr($str,$point-1);
  for ( $index=0; $index<strlen($str); $index++ ) {
    if ( $str[$index] == '(' ) {
      ++$tree;
    }
    else {
      $tree--;
    }
    if ( $tree == 0 ) {
      echo $other + $index+1 . PHP_EOL;
      break;
    }
  }
}
else {
  $str = substr($str,0,$point);
  for ( $index=$point-1; $index>=0; $index-- ) {
    if ( $str[$index] == '(' ) {
      ++$tree;
    }
    else {
      $tree--;
    }
    if ( $tree == 0 ) {
      echo $index +1 . PHP_EOL;
      break;
    }
  }
}