#include <fstream>
#include <vector>
#include <stack>
using namespace std;
struct abc{
    int x; int y; bool f;
}v[500005];
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int grad[100005],n,m;
int ciclu[500005],cnt=0;
vector<int>G[100005];
stack<int>stiva;
int main(){
    fin>>n>>m;
    for(int i=1;i<=m;i++){
        int x,y;
        fin>>x>>y;
        grad[x]++; grad[y]++;
        v[i].x=x; v[i].y=y;
        G[x].push_back(i);
        G[y].push_back(i);
    }
    for(int i=1;i<=n;i++)
    if(grad[i]%2==1){
        fout<<-1;
        return 0;
    }
    stiva.push(1);
    while(!stiva.empty()){
        int nod = stiva.top();
        int ok=0;
        while(G[nod].size()){
            int muchie = G[nod].back();
            G[nod].pop_back();
            if(v[muchie].f == 0){
                v[muchie].f=1;
                ok = 1;
                int x = v[muchie].x;
                int y=v[muchie].y;
                if(x!=nod)
                    stiva.push(x);
                else
                    stiva.push(y);
                break;
            }
        }
        if(ok==0)
            ciclu[++cnt]=nod,stiva.pop();

    }
    if(cnt!=m+1){
        fout<<-1;
        return 0;
    }
    for(int i=1;i<cnt;i++)
        fout<<ciclu[i]<<" ";

    return 0;
}