#include "bits/stdc++.h"

#ifdef WINT_MIN
#define __MAI
#endif

using namespace std;
typedef unsigned int uint;
typedef long long int ll;
typedef unsigned long long int ull;

#define debugv(v) printf("L%d %s => ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;
#define debugm(m) printf("L%d %s is..\n",__LINE__,#m);for(auto v:m){for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) printf("L%d %s is => ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;
#define debugaa(m,w,h) printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[x][y]<<" ";}cout<<endl;}
#define debugaar(m,w,h) printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}
#define ALL(v) (v).begin(),(v).end()
#define repeat(l) for(auto cnt=0;cnt<(l);++cnt)
#define BIGINT 0x7FFFFFFF
#define E107 1000000007ll
void printbit(int u) { if (u == 0)cout << 0; else { int s = 0, k = 0; for (; 0<u; u >>= 1, k++)s = (s << 1) | (u & 1); for (; 0<k--; s >>= 1)cout << (s & 1); } }template<typename T1, typename T2>
    ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << "(" << p.first << ":" << p.second << ")"; return o; }

#define TIME chrono::system_clock::now()
#define MILLISEC(t) (chrono::duration_cast<chrono::milliseconds>(t).count())

namespace {
    std::chrono::system_clock::time_point t;
    void tic() { t = TIME; }
    void toc() { fprintf(stderr, "TIME : %lldms\n", MILLISEC(TIME - t)); }
    std::chrono::system_clock::time_point tle = TIME;
#ifdef __MAI
    void safe_tle(int msec) { assert(MILLISEC(TIME - tle) < msec); }
#else
#define safe_tle(k) ;
#endif
}

#ifndef __MAI 
namespace {
    class MaiScanner {
    public:
        template<typename T>
        void input_integer(T& var) {
            var = 0;
            T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc&&cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var*sign;
        }
        void ign() { getchar_unlocked(); }
        MaiScanner& operator>>(int& var) {
            input_integer<int>(var);
            return *this;
        }
        MaiScanner& operator>>(long long& var) {
            input_integer<long long>(var);
            return *this;
        }
    };
}
MaiScanner scanner;
#else
#define scanner cin
#endif


class Graph {
public:
    size_t n;
    vector<vector<int>> vertex_to;

    Graph(size_t n) :n(n), vertex_to(n) {}

    void connect(int from, int to) {
        vertex_to[from].emplace_back(to);
        vertex_to[to].emplace_back(from);
    }
    void resize(size_t _n) {
        n = _n;
        vertex_to.resize(_n);
    }
};



Graph graph(10000);

int width, height;
int m, n;

vector<int> visit;

void dfs1(int v,int cnt = 1) {
    visit[v] = cnt++;
    for (int u : graph.vertex_to[v]) {
        if (!visit[u]) {
            dfs1(u, cnt);
            return;
        }
    }
    return ;
}
int dfs2(int v, int cnt = -1) {
    visit[v] = cnt--;
    for (int u : graph.vertex_to[v]) {
        if (!visit[u]) {
            return dfs2(u, cnt);
        }
    }
    return v;
}

int main() {
    int i, j, k;
    int x, y, a, b;

    scanner >> n >> m;

    graph.resize(n);
    visit.resize(n);

    int result = 0;
    repeat(m) {
        scanner >> a >> b;
        --a; --b;
        graph.connect(a, b);
    }

    dfs1(0);

    x = dfs2(0);

    a = visit[x];

    vector<int> out;
    out.push_back(x+1);
    while (true) {

        if (a == -1) a = 1;

        ++a;

        i = true;
        for (int u : graph.vertex_to[x]) {
            if (visit[u] == a) {
                x = u;
                i = false;
                break;
            }
        }
        if (i) break;
        out.push_back(x+1);
    }

    printf("%d\n",out.size());
    repeat(out.size()){
        if (cnt != 0) printf(" ");
        printf("%d",out[cnt]);
    }
    cout << endl;

    return 0;
}

Measured memory_bytes: 7312