#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>
 
using namespace std;
 
class InParser {
private:
    const int buff_sz = 16384;

	FILE *fin;
	char *buff;
	int sp;
 
	char read_ch() {
		++sp;
		if (sp == buff_sz) {
			sp = 0;
			fread(buff, 1, buff_sz, fin);
		}
		return buff[sp];
	}
 
public:
	InParser(const char* nume) {
		fin = fopen(nume, "r");
		buff = new char[buff_sz]();
		sp = buff_sz-1;
	}
	
	InParser& operator >> (int &n) {
		char c;
		while (!isdigit(c = read_ch()) && c != '-');
		int sgn = 1;
		if (c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while (isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}
	
	InParser& operator >> (long long &n) {
		char c;
		n = 0;
		while (!isdigit(c = read_ch()) && c != '-');
		long long sgn = 1;
		if (c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while (isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}

    InParser& operator >> (char &c) {
		c = read_ch();
		return *this;
	}
};

InParser fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
 
const int N = 100005;
const int M = 500005;
 
// <destinatie, identificator muchie>
vector<pair<int, int>> g[N];
vector<int> ord;
bool viz[M];
int n, m;
 
void dfs(int nod)
{
    stack<int> st;
 
    st.push(nod);
    while(!st.empty())
    {
        int nod = st.top();
        st.pop();
 
        // am consumat toate muchiile din nod
        if(g[nod].size() == 0)
            ord.push_back(nod);
        else
        {
            int dest = g[nod].back().first;
            int id = g[nod].back().second;
            g[nod].pop_back();
            st.push(nod);
 
            if(!viz[id])
            {
                viz[id] = true;
                st.push(dest);
            }
        }
    }
}
 
int main()
{
	fin >> n >> m;
    for(int i = 0; i < m; i++)
    {
        int x, y;
        fin >> x >> y;
        g[x].push_back({y, i});
        g[y].push_back({x, i});
    }
 
    // verificare
    for(int i = 1; i <= n; i++)
        if(g[i].size() % 2)
        {
            fout << -1;
            return 0;
        }
 
    dfs(1);
 
    ord.pop_back();
    for(int x : ord)
        fout << x << ' ';
 
    return 0;
}