#include <cstdio>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;
const int Nmax = 100005;
int N,M;

vector<int> G[ Nmax ],answer;
stack <int> S;
#define DIM 10000
char buff[DIM];
int poz=0;

void scan(int &numar)
{
     numar = 0;
     //cat timp caracterul din buffer nu e cifra ignor
     while (buff[poz] < '0' || buff[poz] > '9')
          //daca am "golit" bufferul atunci il umplu
          if (++poz == DIM)
               fread(buff,1,DIM,stdin),poz=0;
     //cat timp dau de o cifra recalculez numarul
     while ('0'<=buff[poz] && buff[poz]<='9')
     {
          numar = numar*10 + buff[poz] - '0';
          if (++poz == DIM)
               fread(buff,1,DIM,stdin),poz=0;
     }
}
inline int eulerian(){
    for(int i = 1; i <= N; ++i)
        if(G[i].size() & 1)return 0;
    return 1;
}

inline void read()
{
    scan(N); scan(M);
    int a,b;
    for(int i=1;i<=M;++i)
    {
        scan(a); scan(b);
        G[a].push_back(b);
        G[b].push_back(a);
    }
}



inline void DFS(int nodc) // dfs iterativ
{
    S.push(nodc);
    int y;
    while(!S.empty())
    {
        nodc = S.top();
        if(!G[nodc].size()) // ne intoarcem in stiva
        {
            S.pop();
            answer.push_back(nodc);
        }
        else
        {
            y = G[nodc].back();
            G[nodc].pop_back();
            S.push(y);
            G[y].erase(find(G[y].begin(),G[y].end(),nodc));
        }
    }
}


int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);

    read();
    if(eulerian())
    {
        DFS(1);
        for(int i = 0; i < answer.size() ;++i)
            printf("%d ",answer[i]);
    }
    else
        printf("-1");
    return 0;
}