extern crate maplit;
extern crate sorted_iter;
use maplit::*;
use sorted_iter::SortedPairIterator;
fn main() {
let city = btreemap! {
1 => "New York",
2 => "Tokyo",
};
let country = btreemap! {
1 => "USA",
2 => "Japan",
};
let res: Vec<_> = city.iter().join(country.iter()).collect();
println!("{:?}", res);
}