#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cmath>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <list>
#include <stack>
#include <ctime>
#include <cassert>
using namespace std;

#define PRO "ciclueuler"
void OpenFiles(int EVAL)
{
	if(EVAL)
	{
		char input[100] = PRO, output[100] = PRO;
		freopen(strcat(input, ".in"),"r",stdin);
		freopen(strcat(output,".out"),"w",stdout);
	} else
	{
		freopen("test.in","r",stdin);
		freopen("test.out","w",stdout);
	}
}

#define MAX 100001
#define MOD 666013
#define INF 0xffffff
#define EPS 1E-8

int n, m, nr, grad[MAX];
list<int>graf[MAX];
stack<int>q;

void euler(int x)
{
	int y;
	for(int i=1;i<=n;i++)
		if(grad[i]%2)
		{
			printf("-1");
			return;
		}
	q.push(x);
	while(!q.empty())
	{
		x = q.top();
		if(!graf[x].empty())
		{
			y = graf[x].front();
			graf[x].pop_front();
			for( list<int>::iterator it = graf[y].begin(),end = graf[y].end(); it != end; it++ )
				if( *it == x ){ graf[y].erase(it); break; }
			q.push(y);
		} else {
			nr++;
			if(nr<=m)
				printf("%d ",x);
			q.pop();
		}
	}
}

int main(int argv,char *args[])
{	
OpenFiles(argv==0);
	/* start code */
	scanf("%d %d",&n,&m);
	for(int i=1,x,y;i<=m;i++)
	{
		scanf("%d %d",&x,&y);
		graf[x].push_back(y);
		graf[y].push_back(x);
		grad[x]++;
		grad[y]++;
	}
	euler(1);
	/* end */
	return 0;
}