#include<cstdio>
#include<vector>
#include<stack>
#include<bitset>

#define  pb  push_back
#define NMX 100005

FILE *f=fopen("ciclueuler.in","r");
FILE *g=fopen("ciclueuler.out","w");

using namespace std;

int n,m,numb;
vector <int> G[NMX],sol[NMX];
stack <int> S;
bitset <NMX> used;
bool ok;

void read( void )
{
	fscanf(f,"%d%d",&n,&m);
	for(int i(1) ; i <= m ; ++i )
	{
		int x,y;
		fscanf(f,"%d%d",&x,&y);
		G[x].pb(y);
		G[y].pb(x);		
	}
	fclose(f);	
}

void DFS( int node )
{
	++numb;
	used[node]=true;
	
	for(vector<int> ::iterator it=G[node].begin(); it!=G[node].end() ; ++it )
      if(!used[*it])
		DFS(*it);
	
	
}

int check_euler ( void )
{
	DFS(1);
	if(numb!=n)
	{
		return 1;
	}
	for(int i(1) ; i <= n ; ++i )
		if(G[i].size() % 2 )
			return 1;
	return 0;
}
void del ( int node,int newnode )
{
	G[node].erase(G[node].begin());
	for(vector <int> ::iterator it=G[newnode].begin(); it!=G[newnode].end() ; ++it )
		if( *it == node)
		{
			G[newnode].erase(it);
			return ;
		}
	
}


void euler ( int node )
{
	while( true )
	{
		if( !G[node].size() )
			return ;
		int newnode =G[node].front();
		S.push(node);
		del(node,newnode);
		node=newnode;		
	}	
}

void solve( void )
{
	if(check_euler())
	{
		ok=true;;
		fprintf(g,"-1");
		return ;
	}
	else
	{
		int v=1;
		do
		{
			euler(v);
			v=S.top();
			S.pop();
			sol[0].pb(v);
		}while(!S.empty());
	}
	
	
}
void write( void )
{
	for( vector <int> ::iterator it=sol[0].end()-1;  it!=sol[0].begin()-1; --it )
		fprintf(g,"%d ",*it);
	fclose(g);
	
}


int main ( void )
{
	read();
	solve();
	if( ok == false)
	write();
	return 0;
}