#include <cstdio>
#include <algorithm>
#include <vector>
#include <bitset>
#include <cstdlib>
#include <stack>

#define Nmax 100005

using namespace std;
int N,M,grades[Nmax];
vector<int> G[Nmax],sol;
bitset<Nmax> used;
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 DFS(int k)
{
    used[k] = 1;
    for(vector<int>::iterator it = G[k].begin(); it != G[k].end(); ++it)
        if(!used[*it])
            DFS(*it);
}

void possible_euler()
{
    DFS(1);
    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].erase(G[i].begin());
    for(vector<int>::iterator it = G[j].begin(); it != G[j].end(); ++it)
        if(*it == i)
        {
            G[j].erase(it);
            return;
        }
}

void euler(int k)
{
    S.push(k);
    int nodv;
    while(!S.empty())
    {
        k = S.top();
        while(G[k].size())
        {
            nodv = G[k].front();
            S.push(nodv);
            sterge(k,nodv);
            k = nodv;
        }
        sol.push_back(S.top());
        S.pop();
    }
}
void print()
{
    for(int i = 0; i <(int)sol.size() - 1; ++i)
        printf("%d ",sol[i]);
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);

    read();
    possible_euler();
    euler(1);
    print();

    return 0;
}