#include <bits/stdc++.h>
using namespace std;ifstream fin("ciclueuler.in");ofstream fout("ciclueuler.out");struct muchie{int nod, muchie;};const int NMAX = 1e5+5;int n, m, viz[5*NMAX];vector<muchie>g[NMAX];vector<int>ans;inline void solve(){for(int i = 1; i <= n; ++ i){if(g[i].size()%2==1){fout << -1;return;}}stack<int>st;st.push(1);while(!st.empty()){int node = st.top();st.pop();if(!g[node].size()){ans.push_back(node);}else{int new_node = g[node].back().nod;int new_muchie = g[node].back().muchie;g[node].pop_back();st.push(node);if(!viz[new_muchie]){viz[new_muchie] = 1;st.push(new_node);}}}ans.pop_back();for(auto x : ans)fout << x << ' ';}int main(){fin >> n >> m;for(int i = 1; i <= m; ++ i){int node1, node2;fin >> node1 >> node2;g[node1].push_back({node2,i});g[node2].push_back({node1,i});}solve();}