#include <cstdio>
#include <queue>
#include <stack>
#include <list>
#include <bitset>
#include <stdlib.h>

#define Nmax 100005

using namespace std;
int N,M,grades[Nmax];
list<int> G[Nmax],sol;
bitset<Nmax> used;
queue<int> Q;
stack<int> S;

void read()
{
    scanf("%d%d",&N,&M);
    int a,b;
    for(int i = 1; i <= M; ++i)
    {
        scanf("%d%d",&a,&b);
        G[a].push_back(b);
        G[b].push_back(a);
        grades[a]++;
        grades[b]++;
    }
}

void POSSIBLE_euler()
{
    Q.push(1);
    int k;
    while(!Q.empty())
    {
        k = Q.front();Q.pop();
        used[k] = 1;
        for(list<int>::iterator it = G[k].begin(); it != G[k].end(); ++it)
            if(!used[*it])
                Q.push(*it);
    }
    for(int i = 1; i <= N; ++i)
        if(grades[i]%2 == 1 || !used[i])
        {
            printf("-1\n");
            exit(0);
        }
}

void sterge(int i,int j)
{
    G[i].pop_front();
    for(list<int>::iterator it = G[j].begin(); it != G[j].end(); ++it)
        if(*it == i)
        {
            G[j].erase(it);
            break;
        }
}

void euler(int k)
{
    int nod;
    do
    {
        while(!G[k].empty())
        {
            S.push(k);
            nod = G[k].front();
            sterge(k,nod);
            k = nod;
        }
        k = S.top();
        sol.push_back(k);
        S.pop();
    }while(!S.empty());
}

void print()
{
    for(list<int>::iterator it = sol.begin();it != sol.end();++it)
        printf("%d ",*it);
    printf("\n");
}

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);

    read();
    POSSIBLE_euler();
    euler(1);
    print();

    return 0;
}