#include<cstdio>
#include<algorithm>
#include<vector>
using namespace std;
int N,M,x,y,i,k;
bool viz[100005];
vector <int> G[100005],st;
void dfs(int nod){
viz[nod]=1;
for(i=0;i<(int)G[nod].size();++i)
if(!viz[G[nod][i]])
dfs(G[nod][i]);
}
void euler(int nod){
st.push_back(nod);
while(st.size()){
k=st.back();
if(G[k].size()){
y=G[k].back();
G[k].pop_back();
G[y].erase(find(G[y].begin(),G[y].end(),k));
st.push_back(y);
}else{
printf("%d ",k);
st.pop_back();
}
}
}
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);
}
dfs(1);
for(i=1;i<=N;++i)
if(G[i].size()%2==1||viz[i]==false){
printf("-1");
return 0;
}
euler(1);
return 0;
}