#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>
#include <algorithm>
#include <cstring>
#include <cctype>

#define pb push_back
#define mp make_pair
#define MAXN 100001
#define DIM 8192

using namespace std;

typedef vector<int> graf;

class Reader
{
public:
    Reader(const char* filename)
    {
        f.open(filename);
        pos = 0;
        f.read(buffer,DIM);
    }
    inline Reader& operator >>(int& x)
    {
        x=0;
        sgn=1;
        while((buffer[pos]<'0'||buffer[pos]>'9')&&buffer[pos]!='-')
            if(++pos==DIM)
                f.read(buffer,DIM),pos=0;
        if(buffer[pos]=='-')sgn=-1,pos++;
        while(buffer[pos]>='0'&&buffer[pos]<='9')
        {
            x=x*10+buffer[pos]-'0';
            if(++pos==DIM)f.read(buffer,DIM),pos=0;
        }
        x*=sgn;
        return (*this);
    }
    inline Reader& operator >>(char* c)
    {
        aux = 0;
        while(isspace(buffer[pos]))
            if(++pos==DIM)
                f.read(buffer,DIM),pos=0;
        while(!isspace(buffer[pos]))
        {
            c[aux++]=buffer[pos];
            if(++pos==DIM)f.read(buffer,DIM),pos=0;
        }
        return (*this);
    }
    ~Reader()
    {
        f.close();
    }
private:
    ifstream f;
    int pos,aux,sgn;
    char buffer[DIM];
};

class Writer
{
public:
    Writer(const char* filename)
    {
        g.open(filename);
        pos = 0;
    }
    inline Writer& operator <<(int xx)
    {
        aux = 0;
        x = xx;
        if(xx<0)x=-x;
        if(x==0)
            nr[aux++]='0';
        while(x)
        {
            nr[aux++]=x%10+'0';
            x/=10;
        }
        if(xx<0)nr[aux++]='-';
        while(aux>0)
        {
            buffer[pos++]=nr[--aux];
            if(pos==DIM)g.write(buffer,DIM),pos=0;
        }
        return (*this);
    }
    inline Writer& operator <<(const char* c)
    {
        aux = 0;
        while(c[aux])
        {
            buffer[pos++]=c[aux++];
            if(pos==DIM)g.write(buffer,DIM),pos=0;
        }
        return (*this);
    }
    ~Writer()
    {
        g.write(buffer,pos);
        g.close();
    }
private:
    ofstream g;
    int pos,aux,x;
    char buffer[DIM],nr[21];
};

Reader f("ciclueuler.in");
Writer g("ciclueuler.out");

int n,m,gr[MAXN],a,b,i;
graf G[MAXN],sol;
bitset<MAXN> use;

void sterge(int a, int b)
{
    G[a].erase(find(G[a].begin(),G[a].end(),b));
    G[b].erase(find(G[b].begin(),G[b].end(),a));
}

void euler(int x)
{
    for(graf::iterator it = G[x].begin(); it != G[x].end(); it++)
        sterge(x,*it),
        euler(*it);
    sol.pb(x);
}

int main()
{
    ios_base::sync_with_stdio(false);
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>a>>b;
        gr[a]++;
        gr[b]++;
        G[a].pb(b);
        G[b].pb(a);
    }
    for(i=1;i<=n;i++)
        if(!gr[i]||gr[i]%2) break;
    if(i<=n)
    {
        g<<-1;
        return 0;
    }
    euler(1);
    for(graf::iterator it = sol.begin()+1; it != sol.end(); it++)
        g<<*it<<" ";
    return 0;
}