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

#define Nmax 100005


using namespace std;
int N, M, gr[Nmax];
bitset<Nmax>used;
stack<int> S;
vector<int> G[Nmax];

void read( void )
{
    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);
        ++gr[a];
        ++gr[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 check()
{
    DFS(1);
    for(int i = 1; i <= N; ++i)
        if(!used[i] || gr[i] % 2 == 1)
        {
            printf("-1\n");
            exit(0);
        }
}

void sterge(int x,int y)
{
    G[x].erase(G[x].begin());
    G[y].erase(find(G[y].begin(),G[y].end(),x));
}

void euler(int k)
{
    int v;
    do
    {
        while(G[k].size())
        {
            S.push(k);
            v = k;
            k = G[k][0];
            sterge(v,G[v][0]);
        }
        k = S.top();
        S.pop();
        printf("%d ",k);
    }while(!S.empty());
}

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

    read();
    check();
    euler(1);

    return 0;
}