///////////////////////////// No.22 括弧の対応

    //入力文字読み取り
     var inputall = require('fs').readFileSync('/dev/stdin', 'utf8');

    //すべて受け取り改行で区切って格納
    var input = inputall.split("\n");

    //カッコの総数と求めるカッコの場所
    var brackets_number = input[0].split(" ").map(Number);

    //カッコ
    var brackets = input[1].split("");

    // 2次元配列を作成する
    var brackets_result = new Array(brackets_number[0]/2);
    for (i = 0; i < brackets_result.length; i++) {
        brackets_result[i] = new Array(2);
    }

    for (var i = 0; i < brackets_number[0]; i++) {
        if (brackets[i] == "(") {
           var k =0
            while (true) {
                if (brackets_result[k][0] == undefined) {
                    brackets_result[k][0] = i;
                    break;
                }
                k++
            }
        } else {
            if (brackets[i-1] == "(") {
                brackets_result[k][1] = i;
                k++
                var j = k
            } else {
                while (true) {
                    if (brackets_result[j - 1][1] == undefined) {
                        brackets_result[j - 1][1] = i;
                        break;
                    }
                   j--
                }             
                   
            }
        }
    }

    for (var i =0; i < brackets_result.length; i++) {
        if (brackets_result[i][0] == brackets_number[1]-1) {
            console.log(brackets_result[i][1]+1)
            break;
        } else if(brackets_result[i][1] == brackets_number[1] - 1){
            console.log(brackets_result[i][0]+1)
        }
    }