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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ar array
#define vt vector
#define pq priority_queue
#define pu push
#define pub push_back
#define em emplace
#define emb emplace_back
#define mt make_tuple
#define all(x) x.begin(), x.end()
#define allr(x) x.rbegin(), x.rend()
#define allp(x, l, r) x.begin() + l, x.begin() + r
#define len(x) (int)x.size()
#define uniq(x) unique(all(x)), x.end()
using namespace std;
using namespace __gnu_pbds;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
template <class T, size_t N>
void re(array <T, N>& x);
template <class T>
void re(vt <T>& x);
template <class T>
void re(T& x) {
cin >> x;
}
template <class T, class... M>
void re(T& x, M&... args) {
re(x); re(args...);
}
template <class T>
void re(vt <T>& x) {
for(auto& it : x)
re(it);
}
template <class T, size_t N>
void re(array <T, N>& x) {
for(auto& it : x)
re(it);
}
template <class T, size_t N>
void wr(array <T, N> x);
template <class T>
void wr(vt <T> x);
template <class T>
void wr(T x) {
cout << x;
}
template <class T, class ...M> void wr(T x, M... args) {
wr(x), wr(args...);
}
template <class T>
void wr(vt <T> x) {
for(auto it : x)
wr(it, ' ');
}
template <class T, size_t N>
void wr(array <T, N> x) {
for(auto it : x)
wr(it, ' ');
}
template<class T, class... M>
auto mvt(size_t n, M&&... args) {
if constexpr(sizeof...(args) == 1)
return vector<T>(n, args...);
else
return vector(n, mvt<T>(args...));
}
void set_fixed(int p = 0) {
cout << fixed << setprecision(p);
}
void set_scientific() {
cout << scientific;
}
inline void Open(const string Name) {
#ifndef ONLINE_JUDGE
(void)!freopen((Name + ".in").c_str(), "r", stdin);
(void)!freopen((Name + ".out").c_str(), "w", stdout);
#endif
}
void solve() {
/* standard algorithm */
int n, m; re(n, m);
vt <vt <int>> adj(n);
vt <int> path, marked(m), in(m), out(m);
stack <int> st;
for (int i = 0; i < m; ++i) {
int u, v; re(u, v);
--u, --v;
adj[u].emb(i);
adj[v].emb(i);
in[i] = u;
out[i] = v;
}
/* verify if we have an eulerian path/cycle */
int nr_odd = 0;
for (int i = 0; i < n; i++)
nr_odd += (len(adj[i]) % 2);
if (!(nr_odd == 0 or nr_odd == 2)) {
wr(-1);
return;
}
st.emplace(0);
while (len(st)) {
int u = st.top();
if (len(adj[u]) == 0) {
marked[u] = 1;
path.emb(u);
st.pop();
continue;
}
int e = adj[u].back();
adj[u].pop_back();
int aux = in[e] ^ out[e] ^ u;
if (!marked[e]) {
marked[e] = 1;
st.emplace(aux);
}
}
for (int i = 0; i < len(path) - 1; ++i)
wr(path[i] + 1, ' ');
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
Open("ciclueuler");
int t = 1;
for(;t;t--) {
solve();
}
return 0;
}