#[allow(unused_imports)]
use std::cmp::Ordering;

#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};

#[allow(unused_imports)]
use std::io::{stdin, stdout, BufWriter, Write};

#[allow(unused_imports)]
use std::iter::FromIterator;

#[allow(unused_macros)]
macro_rules! min {
    ($x: expr) => ($x);
    ($x: expr, $($z: expr),+) => {{
        std::cmp::min($x, min!($($z),*))
    }}
}

#[allow(unused_macros)]
macro_rules! max {
    ($x: expr) => ($x);
    ($x: expr, $($z: expr),+) => {{
        std::cmp::max($x, max!($($z),*))
    }}
}

#[allow(unused_macros)]
macro_rules! get {
    ([$t: ty]) => {
        {
            let mut line = String::new();
            stdin().read_line(&mut line).unwrap();
            line.split_whitespace().map(|t|t.parse::<$t>().unwrap()).collect::<Vec<_>>()
        }
    };
    ([$t: ty];$n: expr) => {
        (0..$n).map(|_|get!([$t])).collect::<Vec<_>>()
    };
    ($t: ty) => {
        {
            let mut line = String::new();
            stdin().read_line(&mut line).unwrap();
            line.trim().parse::<$t>().unwrap()
        }
    };
    ($($t: ty),*) => {
        {
            let mut line = String::new();
            stdin().read_line(&mut line).unwrap();
            let mut iter = line.split_whitespace();
            ($(iter.next().unwrap().parse::<$t>().unwrap(),)*)
        }
    };
    ($t: ty; $n: expr) => {
        (0..$n).map(|_|get!($t)).collect::<Vec<_>>()
    };
    ($($t: ty),*; $n: expr) => {
        (0..$n).map(|_|get!($($t),*)).collect::<Vec<_>>()
    };
}

#[allow(unused_macros)]
macro_rules! debug {
    ($($a:expr),*) => {
        #[cfg(debug_assertions)]
        writeln!(&mut std::io::stderr(), concat!("[DEBUG] ", $(stringify!($a), "={:?} "),*), $($a),*).unwrap();
    }
}

const BIG_STACK_SIZE: bool = true;

#[allow(dead_code)]
fn main() {
    use std::thread;
    if BIG_STACK_SIZE {
        thread::Builder::new()
            .stack_size(32 * 1024 * 1024)
            .name("solve".into())
            .spawn(solve)
            .unwrap()
            .join()
            .unwrap();
    } else {
        solve();
    }
}

fn dfs(
    node: usize,
    parent: usize,
    children: &Vec<Vec<usize>>,
    res: &mut BTreeSet<(usize, usize)>,
    outn: &mut Vec<usize>,
) {
    for &child in &children[node] {
        dfs(child, node, children, res, outn);
    }
    if parent == 0 {
        return;
    }
    if outn[node] % 2 == 0 {
        res.insert((parent, node));
        outn[parent] += 1;
    } else {
        res.insert((node, parent));
    }
}

fn solve() {
    let (n, m) = get!(usize, usize);
    let ab = get!(usize, usize; m);

    if m % 2 == 1 {
        println!("-1");
        return;
    }

    let mut nodes = vec![Vec::new(); n + 1];
    for &(a, b) in &ab {
        nodes[a].push(b);
        nodes[b].push(a);
    }

    let mut parent = vec![None; n + 1];
    let mut queue = VecDeque::new();
    queue.push_back(1);
    parent[1] = Some(0);
    let mut children = vec![Vec::new(); n + 1];
    let mut outn = vec![0usize; n + 1];
    while let Some(node) = queue.pop_front() {
        for &next in &nodes[node] {
            if parent[next].is_some() {
                continue;
            }
            children[node].push(next);
            parent[next] = Some(node);
            queue.push_back(next);
        }
    }

    let mut res = BTreeSet::new();
    for &(a, b) in &ab {
        if parent[a].unwrap() != b && parent[b].unwrap() != a {
            res.insert((a, b));
            outn[a] += 1;
        }
    }

    dfs(1, 0, &children, &mut res, &mut outn);
    for (src, dst) in res {
        println!("{} {}", src, dst);
    }
}


Measured memory_bytes: 34172