let count = 0
    let str = s.split('')
    for (let i = 0, j = n - 1; i <= j; i++, j--) {
        if (str[i] !== str[j]) count++
    }
    if (count > k) return -1
    for (let i = 0, j = n - 1; i <= j; i++, j--) {
        if (i === j) {
            if (k > 0) str[i] = '9'; break;
        }
        let available = (k - (str[i] !== '9') - (str[j] !== '9'))
        let needed = (count - (str[i] !== str[j]))
        if (available >= needed) {
            count -= (str[i] !== str[j])
            k -= (str[i] !== '9') + (str[j] !== '9')
            str[i] = '9', str[j] = '9'
        } else {
            if (str[i] != str[j])
                k--, count--;
            str[i] = str[j] = Math.max(str[i], str[j]);
        }
        // console.log(available, needed)
    }
    return str.join('')