#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;
}