#include <bits/stdc++.h>

#define endl '\n'
#define TRACE(x) cerr << #x << " = " << x << endl
#define SZ(x) ((int)x.size())
#define ALL(x) x.begin(), x.end()
#define pb push_back
#define L_B lower_bound
#define U_B upper_bound
//#define LOCAL

using namespace std;
template<class T, class T1> inline bool chkmax(T &x, const T1 &y) { return x < y ? x = y, true : false; }
template<class T, class T1> inline bool chkmin(T &x, const T1 &y) { return x > y ? x = y, true : false; }

double TL = 4.5;
const int MAXN = 100005;

int n, m;
set<int> g[MAXN];

void read() {
    cin >> n >> m;
    if (n != 100000) TL = 4.9;
    for (int i = 1; i <= n; i++) g[i].clear();
    for (int i = 1; i <= m; i++) {
        int u, v;
        cin >> u >> v;
        g[u].insert(v);
        g[v].insert(u);
    }
}

vector<int> max_path, curr_path;
long long max_cost = 0ll;
int timestamp = 0;
int used[MAXN];
bool ap[MAXN];

void dfs(int node, int path_idx, long long curr_cost) {
    used[node] = timestamp;
    curr_path.pb(node);
    int exec = 0;
    for (int nei : g[node]) {
        if (used[nei] != timestamp) {
            exec++;
            dfs(nei, path_idx + 1, curr_cost + nei * path_idx);
        }
    }
    if (!exec && chkmax(max_cost, curr_cost)) max_path = curr_path;
    curr_path.pop_back();
}

int low[MAXN], disc[MAXN];

void init_ap(int node, int parent) {
    static int timer = 0;
    used[node] = timestamp;
    disc[node] = low[node] = ++timer;
    int children = 0;
    for (int nei : g[node]) {
        if (used[nei] == timestamp) chkmin(low[node], disc[nei]);
        else {
            children++;
            init_ap(nei, node);
            if (parent == -1 && children >= 2) ap[node] = true;
            else if (parent != -1 && low[nei] >= disc[node]) ap[node] = true;
            chkmin(low[node], low[nei]);
        }
    }
}

clock_t start;

inline bool time_ok() {
    return ((double)(clock() - start) / (double)CLOCKS_PER_SEC < TL);
}

void solve() {
    memset(used, 0, sizeof(used));
    memset(ap, false, sizeof(ap));
    timestamp++;
    init_ap(1, -1);
    max_path.clear();
    curr_path.clear();
    for (int i = 1; i <= n; i++) {
        if (!time_ok()) break;
        if (!ap[i]) {
            timestamp++;
            dfs(i, 2, i);
        }
    }
    cout << SZ(max_path) << endl;
    for (int node : max_path) cout << node << endl;
}

int main() {
    start = clock();
    #ifndef LOCAL
    freopen("maxpath.in", "rt", stdin);
    freopen("maxpath.out", "wt", stdout);
    #endif // LOCAL
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    read();
    solve();

    return EXIT_SUCCESS;
}