#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <stack>
#include <queue>
#include <map>
#include <string>
#include <cmath>
#include <stdio.h>
using namespace std;

#define lint long long
#define INF 1000000000
#define MOD 1000000007
#define pb push_back
#define mp make_pair

int used[10005];

vector <int> g[10005];
int mxg = -1, mx;
int pp[10005];
int f[10005];

bool cmp(int u, int v) {
    return f[u] < f[v];
}

void dfs(int v, int x) {
    if (x > mx) {
        mx = x;
        mxg = v;
    }
    used[v] = 1;

    for (int i = 0; i < g[v].size(); ++i) {
        int to = g[v][i];
        if (used[to]) continue;
        --f[to];
    }

    sort(g[v].begin(), g[v].end(), cmp);
    for (int i = 0; i < g[v].size(); ++i) {
        int to = g[v][i];
        if (used[to]) continue;
        pp[to] = v;
        dfs(to, x + 1);
    }
}

int st[100005];
int main() {
    int m, n;
    scanf("%d %d", &n, &m);

    for (int i = 0; i < m; ++i) {
        int aa, bb;
        scanf("%d %d", &aa, &bb);
        g[bb].pb(aa);
        g[aa].pb(bb);
        ++f[aa];
        ++f[bb];
    }

    if (n == 1) {
        printf("1\n1");
        return 0;
    }

    mx = -1;
    dfs(1, 1);

    for (int i = 1; i <= n; ++i) {
        used[i] = 0;
    }

    pp[mxg] = -1;
    mx = -1;
    dfs(mxg, 1);

    printf("%d\n", mx);
    while (1) {
        printf("%d ", mxg);
        mxg = pp[mxg];
        if (mxg == -1) break;
    }
    return 0;
}