#include<cstdio>
#include<set>
#include<bitset>
#include<vector>
using namespace std;
const int NMAX = 100005;
int N,M,X,Y,i;
vector<int> V[NMAX];
vector<int> St;
bitset<NMAX> viz;
void DFS(int X)
{
    for(vector<int>::iterator it=V[X].begin();it!=V[X].end();it++)
        if(!viz[*it])
        {
            viz[*it]=1;
            DFS(*it);
        }
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d%d",&N,&M);
    for(;M;M--)
    {
        scanf("%d%d",&X,&Y);
        V[X].push_back(Y); V[Y].push_back(X);
    }
    for(i=1;i<=N;i++) if(V[i].size()&1) {printf("-1\n"); return 0;}
    viz[1]=1; DFS(1);
    for(i=1;i<=N;i++) if(!viz[i]) {printf("-1\n"); return 0;}
    St.push_back(1);
    while(!St.empty())
    {
        X=St.back();
        if(V[X].size())
        {
            Y=V[X].back();
            V[X].pop_back();
            for(vector<int>::iterator it=V[Y].begin();it!=V[Y].end();it++)
                if(*it==X) {*it=V[Y].back(); V[Y].pop_back(); break;}
            St.push_back(Y);
        }
        else
        {
            printf("%d ",St.back());
            St.pop_back();
        }
    }
    return 0;
}