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<pi> > A(N_MAX);
int stv[1<<19],nr[1<<19],Q[N_MAX],V[N_MAX];
bool viz[N_MAX];

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

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);
		int poz = find(x,y);
		if(poz==-1)
		{
			A[x].pb( mp(y,1) );
			A[y].pb( mp(x,1) );
		}
		else
		{
			++A[x][poz].s;
			++A[y][ find(y,x) ].s;
		}	
		if(x==y)
			++V[x];
	}	
}

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

			--A[nod][i].s;
			stv[++top] = fiu;
		}	
		
		viz[nod] = true;
		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;
}