#include<fstream>
#include<vector>
using namespace std;
#define maxn 100005
#define maxm 500005
int n,m,g[maxn],stiva[maxm],rez[maxm] , prim=1, ultim=1,k=1;
vector <int>v[maxn];
ifstream cin("ciclueuler.in");
ofstream cout("ciclueuler.out");

void read(){
    int x,y;
    for(int i=1; i<=m; i++){
        cin>>x>>y;
        if(x==y){
            v[x].push_back(y);
            g[x]++;
        } else{
        v[x].push_back(y);
        v[y].push_back(x);
        g[x]++; g[y]++;
    }
    }
}

void euler(){
    int x=prim;
    while(prim<=ultim){
        while(g[stiva[x]]){
            stiva[++ultim]=v[stiva[x]][g[stiva[x]]-1];
            //cout<<v[stiva[x]][g[stiva[x]]-1]<<' ';
            v[stiva[x]].pop_back();
            g[stiva[x]]--;
            if(stiva[x]!=stiva[ultim]){
            for(int i=0; i<g[stiva[ultim]]; i++){
                if(v[stiva[ultim]][i]==stiva[x]){
                    v[stiva[ultim]].erase (v[stiva[ultim]].begin()+i);
                    g[stiva[ultim]]--;
                    break;
                }
            }
            }
            prim++;
            euler();
        }
        prim++;
        rez[k++]=stiva[x];
    }
}


int main(){
    cin>>n>>m;
    read();
    stiva[1]=1;
    euler();
    k-=2;
    if(k!=m)
       cout<<-1;
    else
    for(int i=1; i<=k; i++)
        cout<<rez[i]<<' ';
    return 0;
}
/*
4 6
1 2
1 3
2 2
2 3
3 4
3 4
*/