/*
    Look at me!
    Look at me!
    The monster inside me has grown this big!
*/
  
#include<fstream>
#include<iostream>
#include<cstdio>
#include<map>
#include<set>
#define FIT(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<bitset>
#include<cmath>
#include<iomanip>
#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 long long
#define inf 1<<30
#define eps 1.e-10
#define N 500100
#define mod 1999999973
using namespace std;
/*int dx[]={0,0,0,1,-1};
int dy[]={0,1,-1,0,0};*/
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
vector<pii> v[N];
stack<int> st;
int n,m,x,y,E[N],e,viz[N],gr[N];
void dfs(int x)
{
	viz[x]=1;
	FIT(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())
	{
		if(!v[st.top()].size())
		{
			E[++e]=st.top();
			st.pop();
		}
		else
		{
			x=st.top();
			pii muchie=v[x][v[x].size()-1];
			if(viz[muchie.se])
				v[x].pop_back();
			else
			{
				st.push(muchie.fi);
				viz[muchie.se]=1;
				v[x].pop_back();
			}
		}
	}
	--e;
	FOR(i,1,e)
	g<<E[i]<<" ";
    return 0;
}