using namespace std;

#include <bitset>
#include <vector>

#define pb push_back
#define sz size
#define f first
#define s second
#define II inline
#define FOR(i,a,b) for(int i=a;i<=b;++i)
#define mp make_pair
#define IN  "ciclueuler.in"
#define OUT "ciclueuler.out"
#define N_MAX 1<<17

int last,N,M;
typedef pair<int,int> pi;
vector< vector<int> > A(N_MAX);
int stv[1<<19],nr[1<<19],Q[1<<19];

II void scan()
{
	freopen(IN,"r",stdin);
	freopen(OUT,"w",stdout);
	scanf("%d %d",&N,&M);
	
	int x,y;
	FOR(i,1,M)
	{
		scanf("%d %d",&x,&y);
		
		A[x].pb(y);
		A[y].pb(x);
	}	
}

II int find(int x,int y)
{
	FOR(i,0,(int)A[x].sz()-1)
		if(A[x][i] == y)
			return i;
	return -1;	
}

II void euler()
{
	int i,top(0),fiu,nod(1);
	
	for(stv[++top] = 1;nod;)
	{
		for(;nr[top] < (int)A[ stv[top] ].sz();)
		{
			i = nr[top]++;
			nod = stv[top];
			fiu = A[nod][i];
			
			if(!fiu)
				continue;
			
			stv[++top] = fiu;
			A[fiu][ find(fiu,nod) ] = A[nod][i] = 0;
		}	
		
		Q[++last] = nod;
		
		nr[top] = 0;
		nod = stv[--top];
	}	
}

II void print()
{
	if(--last < M)
	{
		printf("-1\n");
		return;
	}
	FOR(i,1,last)
		printf("%d ",Q[i]);
}

int main()
{
	scan();
	euler();
	print();
	return 0;
}