#include<cstdio>
#include<algorithm>
#include<vector>
#include<stack>
#define maxn 100005
using namespace std;
stack <int> stiv;
vector <int> G[maxn];
int x,y,n,m,ok=1;
void Fleury(){
    int x,y;
    stiv.push(1);
    while(stiv.size()){
        x=stiv.top();
        if(G[x].size()==0){
            printf("%d ",x);
            stiv.pop();
        }
        else{
            y=*G[x].begin();
            G[x].erase(G[x].begin());
            G[y].erase(find(G[y].begin(),G[y].end(),x));
            stiv.push(y);
        }
    }

}
int main(){
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d%d", &n,&m);
    for(int i=1;i<=m;++i){
       scanf("%d%d", &x, &y);
       G[x].push_back(y);
       G[y].push_back(x);
    }
    for(int i=1;i<=n;++i)
    if(G[i].size() %2){
        ok=0;
        printf("-1");
        break;
    }
    if(ok)
        Fleury();
    return 0;
}