11111111

sortLetterStr = (letterStr) => {

    let arr = new Array();

    for (let i = 0; i < letterStr.length; ++i) {

        arr.push(letterStr[i].charCodeAt());

    }

    arr.sort((x, y) => (x - y));

    let res = "";

    for (let i = 0; i < arr.length; ++i) {

        let x = arr[i];

        let A = 'A'.charCodeAt();

        let Z = 'Z'.charCodeAt();

        let a = 'a'.charCodeAt();

        let val = 0;

        if (x >= A && x <= Z) {

            val = x - A;

        } else {

            val = x - a;

        }

        val = (val + 1) * (val + 1) % 26;

        if (x >= A && x <= Z) {

            res += String.fromCharCode(val + A);

        } else {

            res += String.fromCharCode(val + a);

        }

    }

    return res;

};