/*
    Those without power, seek us!
    Those with power, fear us!
    We are the Order of the Black Knights!
*/

#include<fstream>
#include<cstdio>
#include<map>
#include<set>
#define FIT(a,b) for(vector<int >::iterator a=b.begin();a!=b.end();a++)
#define FITP(a,b) for(vector<pair<int,int> >::iterator a=b.begin();a!=b.end();a++)
#define RIT(a,b) for(vector<int>::reverse_iterator a=b.end();a!=b.begin();++a)
#include<stack>
#define ROF(a,b,c) for(int a=b;a>=c;--a)
#include<vector>
#include<algorithm>
#define FOR(a,b,c) for(int a=b;a<=c;++a)
#define REP(a,b) for(register int a=0;a<b;++a)
#include<cstring>
#include<ctime>
#include<bitset>
#include<cmath>
#include<iomanip>
#include<set>
#define f cin
#define g cout
#include<queue>
#define debug cerr<<"OK";
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define ll long long
#define ull unsigned int
#define mod 1000000009LL
#define SQR 350
#define db double
#define inf 1<<30
#define div fdasfasd
#define hash dsafdsfds
#define od 100003
#define mod 666013
#define DIM 60010000
#define base 256
#define bas 255
#define N 100100
#define M 500100
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
/*
    int dx[]={0,0,0,1,-1};
    int dy[]={0,1,-1,0,0};
*/
stack<int> st;
vector<pii > v[N];
int te,n,m,x,y,E[M],gr[N],viz[M];
void dfs(int x)
{
    viz[x]=1;
    FITP(it,v[x])
    if(!viz[it->fi])
        dfs(it->fi);
}
int main ()
{
    f>>n>>m;
    FOR(i,1,m)
    {
        f>>x>>y;
        v[x].pb(mp(y,i));
        v[y].pb(mp(x,i));
        gr[x]++;
        gr[y]++;
    }
    dfs(1);
    FOR(i,1,n)
    if(!viz[i]||gr[i]%2)
    {
        g<<"-1";
        return 0;
    }
    st.push(1);
    memset(viz,0,sizeof(viz));
    while(!st.empty())
    {
        int x=st.top();
        if(v[x].empty())
        {
            E[++te]=x;
            st.pop();
        }
        else
        {
            pii y=v[x][v[x].size()-1];
            v[x].pop_back();
            if(viz[y.se])
                continue;
            viz[y.se]=1;
            st.push(y.fi);
        }
    }
    FOR(i,1,te-1)
    g<<E[i]<<" ";
    return 0;
}