#include <bits/stdc++.h>

using namespace std;

//#define f cin
//#define g cout
//#define INF 1000000000000000003
//#define ll long long
#define NMax 100005

ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

int n,m,x,y;
int grad[NMax];
vector<int> G[NMax];
stack<int> st;

void elimin(int u, int v){
    for(int i = 0; i < G[u].size(); ++i){
        if(G[u][i] == v){
            G[u].erase(G[u].begin() + i);
            return;
        }
    }
}
int main()
{
    f >> n >> m;
    for(int i = 1; i <= m; ++i){
        f >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
        grad[x] ++;
        grad[y] ++;
    }

    for(int i = 1; i <= n; ++i){
        if(grad[i] % 2 != 0){
            g << -1 << '\n';
            return 0;
        }
    }

    st.push(1);
    int k = 0;
    while(!st.empty()){
        int nod = st.top();

        if(G[nod].size() == 0){
            if(k++ == m){
                break;
            }
            g << nod << ' ';
            st.pop();
        }else{
            int v = G[nod][G[nod].size() - 1];
            G[nod].pop_back();
            elimin(v, nod);
            st.push(v);
        }
    }
    return 0;
}