#include <bits/stdc++.h>
#define ff first
#define ss second

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;

const string file = "ciclueuler";
const ll INF = 9223372036854775807ll;
const int inf = 2147483647, nmax = 100005;

int n, m;
vector<int> v[nmax], sol;
bool ok[nmax*5];
pi e[nmax*5];

class InParser {
private:
    FILE *fin;
    char *buff;
    int sp;

    char read_ch() {
        ++sp;
        if (sp == 4096) {
            sp = 0;
            fread(buff, 1, 4096, fin);
        }
        return buff[sp];
    }

public:
    InParser(const char* nume) {
        fin = fopen(nume, "r");
        buff = new char[4096]();
        sp = 4095;
    }

    InParser& operator >> (int &n) {
        char c;
        while (!isdigit(c = read_ch()) && c != '-');
        int sgn = 1;
        if (c == '-') {
            n = 0;
            sgn = -1;
        } else {
            n = c - '0';
        }
        while (isdigit(c = read_ch())) {
            n = 10 * n + c - '0';
        }
        n *= sgn;
        return *this;
    }
};

class OutParser {
private:
    FILE *fout;
    char *buff;
    int sp;

    void write_ch(char ch) {
        if (sp == 50000) {
            fwrite(buff, 1, 50000, fout);
            sp = 0;
            buff[sp++] = ch;
        } else {
            buff[sp++] = ch;
        }
    }


public:
    OutParser(const char* name) {
        fout = fopen(name, "w");
        buff = new char[50000]();
        sp = 0;
    }
    ~OutParser() {
        fwrite(buff, 1, sp, fout);
        fclose(fout);
    }

    OutParser& operator << (int vu32) {
        if(vu32 == -1){
            write_ch('-');
            write_ch('1');
        } else if (vu32 <= 9) {
            write_ch(vu32 + '0');
        } else {
            (*this) << (vu32 / 10);
            write_ch(vu32 % 10 + '0');
        }
        return *this;
    }

    OutParser& operator << (char ch) {
        write_ch(ch);
        return *this;
    }
    OutParser& operator << (const char *ch) {
        while (*ch) {
            write_ch(*ch);
            ++ch;
        }
        return *this;
    }
};


void dfs(int x)
{
    for (int i = v[x].size()-1; i >= 0; --i)
        if(!ok[v[x][i]]){
            ok[v[x][i]] = 1;
            int y = e[v[x][i]].ff;
            if(y == x)
                y = e[v[x][i]].ss;
            dfs(y);
        }
    sol.push_back(x);
}

int main()
{
    InParser fin ("ciclueuler.in");
    OutParser fout ("ciclueuler.out");
    fin >> n >> m;
    for (int i = 1; i <= m; ++i){
        int x, y;
        fin >> x >> y;
        e[i] = {x, y};
        v[x].push_back(i);
        v[y].push_back(i);
    }
    bool any = false;
    for (int i = 1; i <= n; ++i)
        if(v[i].size()%2 == 1)
            any = true;
    if(any){
        fout << "-1";
        return 0;
    }
    dfs(1);
    sol.pop_back();

    for (auto x : sol)
        fout << x << " ";
    return 0;
}