#include<fstream>
#include<cstdio>
#include<set>
#include<stack>
#include<vector>
#include<algorithm>
#define FOR(a,b,c) for(int a=b;a<=c;++a)
#include<cstring>
#include<bitset>
#include<cmath>
#include<iomanip>
#include<queue>
#define f cin
#define g cout
#define mp make_pair
#define pb push_back
#define ll long long
#define inf (1<<30)
#define base 256
#define ba 255
#define N 100100
#define EPS 1e-12
#define mod  98999
#define inu "ciclueuler.in"
#define outu "ciclueuler.out"
using namespace std;
ifstream f(inu);
ofstream g(outu);
//int dx[]={0,0,0,1,-1};
//int dy[]={0,1,-1,0,0};
vector<pair<int,int> > v[N];
pair<int,int> muchie;
stack<int> st;
int E[N*5],n,m,e,x,y,nod,used[N*5],viz[N];
void dfs(int x)
{
	viz[x]=1;
	for(int i=0;i<v[x].size();++i)
		if(!viz[v[x][i].second])
			dfs(v[x][i].second);
}
int main ()
{
	f>>n>>m;
	FOR(i,1,m)
	{
		f>>x>>y;
		v[x].pb(mp(y,i));
		v[y].pb(mp(x,i));
	}
	dfs(1);
	FOR(i,1,n)
	if((v[i].size()%2)||!viz[i])
	{
		g<<"-1";
		return 0;
	}
	st.push(1);
	while(!st.empty())
	{
		nod=st.top();
		if(!v[nod].size())
		{
			E[++e]=nod;
			st.pop();
		}
		else
		{
			pair<int,int> muchie;
			muchie=v[nod][v[nod].size()-1];
			if(used[muchie.second])
				v[nod].pop_back();
			else
			{
				used[muchie.second]=1;
				st.push(muchie.first);
			}
		}
	}
	FOR(i,2,e)
	g<<E[i]<<" ";
    return 0;
}