#include<cstdio>
#include<vector>
using namespace std;
int N,M,x,y,rez[100001];
vector <int> G[100001];
void stergere_muchii(int start){
    y=G[start][0],G[start].erase(G[start].begin());
    bool ok=1;
    for(int i=0;i<G[y].size()&&ok;++i)
            if(G[y][i]==start)
                ok=0,G[y].erase(G[y].begin()+i);
}
void euler(int nod){
    while(G[nod].size()){
        stergere_muchii(nod);
        euler(y);
    }
    rez[++x]=nod;
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d%d",&N,&M);
    while(M--){
        scanf("%d%d",&x,&y);
        G[x].push_back(y),G[y].push_back(x);
    }
    bool ok=1;
    for(int i=1;i<=N&&ok;++i)
        if(G[i].size()%2)
                printf("-1"),ok=0;
    if(ok){
        x=0;
        euler(1);
        for(int i=x;i>=2;--i)printf("%d ",rez[i]);
    }
    return 0;
}