use std::{
    collections::{BTreeSet, HashMap},
    io::Read,
    iter::repeat,
};

fn main() {
    let mut input = String::new();
    std::io::stdin().read_to_string(&mut input).unwrap();

    let mut lines = input.lines();
    let mut nm = lines.next().unwrap().split_ascii_whitespace();
    let n: usize = nm.next().unwrap().parse().unwrap();
    let m: usize = nm.next().unwrap().parse().unwrap();

    let mut covers = HashMap::<usize, Vec<usize>>::with_capacity(m);
    let mut n_above = vec![0usize; n];
    let mut sticks_at: Vec<BTreeSet<usize>> = repeat(BTreeSet::new()).take(m).collect();

    for i in 0..n {
        sticks_at[0].insert(i);
    }

    for mut line in lines.map(str::split_ascii_whitespace) {
        let a = line.next().unwrap().parse::<usize>().unwrap() - 1;
        let b = line.next().unwrap().parse::<usize>().unwrap() - 1;

        covers.entry(a).or_default().push(b);
        sticks_at[n_above[b]].remove(&b);
        n_above[b] += 1;
        sticks_at[n_above[b]].insert(b);
    }

    let mut picks = Vec::with_capacity(n);
    loop {
        let stick = if let Some(&s) = sticks_at[0].iter().next() {
            s
        } else {
            break;
        };
        sticks_at[0].remove(&stick);
        picks.push(stick);

        if let Some(c) = covers.get(&stick) {
            for &b in c {
                sticks_at[n_above[b]].remove(&b);
                n_above[b] -= 1;
                sticks_at[n_above[b]].insert(b);
            }
        }
    }

    if picks.len() != n {
        println!("IMPOSSIBLE");
        return;
    }

    for p in picks {
        println!("{}", p + 1);
    }
}