#include <bits/stdc++.h>

using namespace std;

unsigned int N, M;
unsigned int u, v;

const int MAX=100001;
vector <int> G[MAX], H[MAX];
deque <int> Q;
bool seen[MAX*5];
unsigned int degree[MAX];
unsigned int node, x, y;
unsigned int i;

int main ()
{
    freopen("ciclueuler.in","r",stdin);
    scanf("%d %d",&N,&M);
    for (i=1; i<=M; i++)
    {
        scanf("%d %d",&u,&v);
        G[u].push_back(v);
        G[v].push_back(u);
        H[u].push_back(i);
        H[v].push_back(i);
        degree[u]++;
        degree[v]++;
    }
    freopen("ciclueuler.out","w",stdout);
    for (i=1; i<=N; i++)
        if (degree[i]&1 == 1)
        {
            printf("-1");
            return 0;
        }
    Q.push_back(1);
    while (!Q.empty())
    {
        node = Q.back();
        if (degree[node] == 0)
        {
            printf("%d ",node);
            Q.pop_back();
        }
        else
        {
            x = G[node].back();
            y = H[node].back();
            G[node].pop_back();
            H[node].pop_back();
            if (seen[y] == 0)
            {
                seen[y] = 1;
                Q.push_back(x);
                degree[x]--;
                degree[node]--;
            }
        }
    }
    return 0;
}