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

#define rep(i, a, b) for (auto i = a; i < (b); ++i)
#define repr(i, a, b) for (auto i = (a) - 1; i >= (b); --i)
#define pb push_back
#define eb emplace_back
#define all(x) begin(x), end(x)
#define sz(x) int((x).size())

using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;
using vii = vector<pii>;

template<class T>
inline bool cmax(T &a, const T &b) {
    return a < b ? a = b, 1 : 0;
}

template<class T>
inline bool cmin(T &a, const T &b) {
    return b < a ? a = b, 1 : 0;
}

const int inf = 0x3f3f3f3f;
const ll linf = 1e18;
const double dinf = numeric_limits<double>::infinity();

struct UF {
    vi e;
    UF(int n) : e(n, -1) {}
    bool sameSet(int a, int b) {
        return find(a) == find(b);
    }
    int find(int x) {
        return e[x] < 0 ? x : e[x] = find(e[x]);
    }
    bool join(int a, int b) {
        a = find(a), b = find(b);
        if (a == b)
            return false;
        if (e[a] > e[b])
            swap(a, b);
        e[a] += e[b];
        e[b] = a;
        return true;
    }
};

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    
    int n, m;
    cin >> n >> m;
    vector<vi> g(n + 1);
    UF uf(n + 1);
    rep(i, 0, m) {
        int u, v;
        cin >> u >> v;
        if (!uf.sameSet(u, v)) {
            uf.join(u, v);
            g[u].pb(v);
            g[v].pb(u);
        }
    }

    vi ans;
    auto dfs = [&](auto &&self, int u, int p, int t) -> void {
        if (!t) {
            ans.pb(u);
        }
        for (auto &v : g[u]) {
            if (v != p) {
                self(self, v, u, 1 - t);
            }
        }
        if (t) {
            ans.pb(u);
        }
    };
    dfs(dfs, 1, -1, 0);

    for (auto &x : ans) {
        cout << x << ' ';
    }
    cout << '\n';

    return 0;
}