#include <cstdio>
#include <iostream>
#include <fstream>
#include <algorithm>
#include <cmath>
#include <set>
#include <vector>
#include <queue>
#include <iomanip>
#include <cstring>
#include <stack>

#define INF 0x3f3f3f3f
#define NMax 100005
using namespace std;

vector<int> vecini[NMax];
stack<int> s;
int n,m,x,y;
int grad[NMax];

void elimina(int v,int u){
    for(int i = 0; i < vecini[v].size(); ++i){
        if(vecini[v][i] == u){
            vecini[v].erase(vecini[v].begin() + i);
            return;
        }
    }
}
void euler(){
    s.push(1);
    int k = 0;
    while(!s.empty()){
        int nod = s.top();
        if(k >= m)
            break;
        if(!vecini[nod].size()){
            printf("%d ",nod);
            k++;
            s.pop();
        }else{
            int v = vecini[nod].back();
            vecini[nod].pop_back();
            elimina(v,nod);
            s.push(v);
        }
    }
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i = 0; i < m; ++i){
        scanf("%d%d",&x,&y);
        vecini[x].push_back(y);
        vecini[y].push_back(x);
        grad[x] ++;
        grad[y] ++;
    }
    for(int i = 1; i <= n; ++i){
        if(grad[i] % 2){
            printf("-1");
            return 0;
        }
    }
    euler();
    return 0;
}