<?php
$input_lines = trim(fgets(STDIN));
$input_lines = str_replace(array("\r\n","\r","\n"), "", $input_lines);
do {
    $tmpStr[] = $input_lines;
    $input_lines = trim(fgets(STDIN));
    $input_lines = str_replace(array("\r\n","\r","\n"), "", $input_lines);
} while ($input_lines !== "");

$tmp = $tmpStr[1];
$tmpPos = explode(" ",$tmpStr[0])[1];
$s = str_split($tmp);

$tmpCnt = 0;
if($s[$tmpPos - 1] === "("){
	$max = count($s);
	
	for($i = $tmpPos - 1;$i < $max ;$i++){
		$tmpCnt += getCountVal($s[$i]);
		
		if($tmpCnt === 0){
			break;
		}
	}
}else{
	for($i = $tmpPos - 1;$i >= 0 ;$i--){
		$tmpCnt += getCountVal($s[$i]);
		
		if($tmpCnt === 0){
			break;
		}
	}
}

print $i + 1;

function getCountVal($i_string){
		if($i_string === "("){
			return 1;
		}else{
			return -1;
		}
}