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

const int N = 100010;
int n, m;
vector <int> sol, v[N];
stack <int> S;
struct edge{
    int a, b, c;
} M[5*N];

int next(edge A, int nodcr){
    if (nodcr == A.a) return A.b;
    else return A.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, 1};
    }
    for (int i=1; i<=n; i++){
        if (v[i].size() & 1) return cout << -1, 0;
    }
    S.push(1);
    while (!S.empty()){
        int nod = S.top();
        int i = v[nod].size() - 1;
        while (i >= 0 && !M[v[nod][i]].c) v[nod].pop_back(), i--;
        if (!v[nod].size()) sol.push_back(nod), S.pop();
        else M[v[nod][i]].c = 0, S.push(next(M[v[nod][i]], nod)), v[nod].pop_back();
    }
    sol.pop_back();
    for (auto it: sol) cout << it << " ";
    return 0;
}