#include<fstream>
#include<vector>
using namespace std;
ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");
const int N=100020;
vector<int>a[N];
vector<int>poz[N];
vector<bool>folosit[N];
int m,n,v[N],nr;
void read()
{
	int x,y,i;
	in>>n>>m;
	for(i=0;i<m;i++)
	{
		in>>x>>y;
		a[x].push_back(y);
		a[y].push_back(x);
		poz[x].push_back(a[y].size()-1);
		poz[y].push_back(a[x].size()-1);
		folosit[x].push_back(false);
		folosit[y].push_back(false);
	}
}
int y;
void euler(int x)
{
	
	for(int i=0;i<a[x].size();i++)
	{
		if(folosit[x][i])
			continue;
		y=a[x][i];
		folosit[x][i]=1;
		folosit[y][poz[x][i]]=1;
		euler(y);
	}
	//if(nr<=n+1)
	v[++nr]=x;
}
void afis()
{
	if(nr!=m+1 || v[nr]!=v[1])
	{
		out<<-1;
		return;
	}
	for(int i=1;i<nr;i++)
		out<<v[i]<<" ";
}
int main()
{
	read();
	euler(1);
	afis();
	return 0;
}