#include<fstream>
#include<vector>
#include<stack>

#define maxn 100005
#define maxm 500005
#define pb push_back
#define mp make_pair

using namespace std;

ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

int n,m,e;
int gr[maxn],used[maxm],viz[maxn],E[maxm];
stack<int>St;
vector< pair<int,int> >G[maxn];

inline void citire () {
	
	f >> n >> m;
	
	int x,y;
	for ( int i = 1 ; i <= m ; ++i ){
		f >> x >> y;
		G[x].pb(mp(y,i));
		G[y].pb(mp(x,i));
		++gr[x]; ++gr[y];
	}
}

void dfs ( int nod ){
	viz[nod] = 1;
	
	for ( vector< pair<int,int> >::iterator itt = G[nod].begin() ; itt != G[nod].end() ; ++itt ){
		int nodvcn = itt->first;
		if ( !viz[nodvcn] ){
			dfs(nodvcn);
		}
	}
}

inline void euler () {
	
	int start = 0,sol = 1;
	for ( int i = 1 ; i <= n ; ++i ){
		if ( gr[i] ){
			start = i;
			dfs(i);
		}
	}
	
	for ( int i = 1 ; i <= n ; ++i ){
		if ( (gr[i]&1) || (gr[i]&&!viz[i]) ){
			sol = 0;
		}
	}
	
	if ( !sol ){
		g << "-1\n";
		return ;
	}
	
	St.push(start);
	while ( !St.empty() ){
		int nod = St.top();
		
		if ( G[nod].empty() ){
			E[++e] = nod;
			St.pop();
		}
		else{
			pair<int,int>edge = G[nod][G[nod].size()-1];
			if ( used[edge.second] ){
				G[nod].pop_back();
			}
			else{
				used[edge.second] = 1;
				St.push(edge.first);
				G[nod].pop_back();
			}
		}
	}
	
	for ( int i = 1 ; i < e ; ++i ){
		g << E[i] << " ";
	}
	g << "\n";
}

int main () {
	
	citire();
	euler();
	
	f.close();
	g.close();
	
	return 0;
}