fn biggerIsGreater(w: &str) -> String {
    let length = w.len();
    let mut temp = w.chars().collect::<Vec<char>>();
    let mut i = None; //
    let mut idx: Option<usize> = None;
    let mut smallest = 'z';

    for a in (0..length - 1).rev() {
        if temp[a] < temp[a + 1] {
            i = Some(a);
            break;
    }
}
    if let Some(i) = i {
    let mut j = i + 1;
    for k in i + 1..length {
    if temp[k] > temp[i] && (j == i + 1 || temp[k] < temp[j]) {
        idx = Some(k);
    }
}
        if let Some(j) = idx {
            temp.swap(i, j);
            temp[i + 1..].sort();
        }
        temp.iter().collect()
    } else {
        "no answer".into()
    }
}