#include <bits/stdc++.h>
using namespace std;

#define N 100005
struct edge{
    int a, b;
    bool c;
} M[5*N];
int n, m, st[5*N], vf;
vector <int> v[N], sol;

int nxt(int cur, int idx){
    if (cur == M[idx].a) return M[idx].b;
    return M[idx].a;
}

int main(){
    ifstream cin ("ciclueuler.in");
    ofstream cout ("ciclueuler.out");
    cin >> n >> m;
    for (int i=1, x, y; i<=m; i++){
        cin >> x >> y;
        v[x].push_back(i);
        v[y].push_back(i);
        M[i] = {x, y, 0};
    }
    for (int i=1; i<=n; i++)
        if (v[i].size() & 1) return cout << -1, 0;
    st[++vf] = 1;
    while (vf){
        int nod = st[vf];
        int i = v[nod].size() - 1;
        while (i>=0 && M[v[nod][i]].c) v[nod].pop_back(), i--;
        if (i >= 0) st[++vf] = nxt(nod, v[nod][i]), M[v[nod][i]].c = 1, v[nod].pop_back();
        else sol.push_back(nod), vf--;
    }
    sol.pop_back();
    for (auto it: sol) cout << it << ' ';
    return 0;
}