#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> ii;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef vector<ii> vii;

#define x first
#define y second
#define pb push_back
#define eb emplace_back
#define all(v) (v).begin(), (v).end()

vvi adj;
vector<bool> visited;

void dfs(ll i, bool c) {
	if (visited[i]) return;
	visited[i] = true;
	if (c) cout << i+1 << " ";
	for (ll j : adj[i]) dfs(j, !c);
	if (!c) cout << i+1 << " ";
}

void run() {
	ll n, m;
	cin >> n >> m;
	adj = vvi(n);
	visited = vector<bool>(n, false);
	for (ll i = 0; i < m; i++) {
		ll x, y;
		cin >> x >> y;
		x--; y--;
		adj[x].pb(y); adj[y].pb(x);
	}
	dfs(0, true);
	cout << endl;
}

signed main() {
    ios_base::sync_with_stdio(false); cin.tie(0);
    run();
    return 0;
}