#include <bits/stdc++.h>
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
const int nMax = 100003;
const int mMax = 500003;
vector <int>  Graf[nMax];
int st[mMax], dr[mMax], ans[mMax];
int n, m, k;
bool used[mMax];
inline bool Euler() {
    for(int i = 1; i <= n; i++) {
        if(Graf[i].size() & 1) {
            return 0;
        }
    }
    return 1;
}

inline void Dfs(int node) {

    for(auto i : Graf[node]) {
        if(!used[i]) {
            used[i] = 1;
            Dfs(st[i] + dr[i] - node);
        }
    }
    ans[++k] = node;
}

int main()
{
    f >> n >> m;
    for(int i = 1; i <= m; i++) {
        f>> st[i] >> dr[i];
        Graf[st[i]].push_back(i);
        Graf[dr[i]].push_back(i);
    }
    if(!Euler()) {
        g<< "-1\n";
        return 0;
    }
    Dfs(1);
    for(int i = 1; i <= k; i++) {
        g<< ans[i] << " ";
    }
    return 0;
}