#![allow(unused_variables)]
fn main() {
    use std::collections::BTreeSet;
    let mut a = BTreeSet::new();
    a.insert(1);
    a.insert(2);
    a.insert(3);
    a.insert(17);
    a.insert(41);
    let b = a.split_off(&3);
    assert_eq!(a.len(), 2);
    assert_eq!(b.len(), 3);
    assert!(a.contains(& 1));
    assert!(a.contains(& 2));
    assert!(b.contains(& 3));
    assert!(b.contains(& 17));
    assert!(b.contains(& 41));
}