#include<cstdio>
#include<vector>
#include<bitset>
using namespace std;
const int nmax = 100005;
int n,m,x,y,i;
vector<int> v[nmax],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].empty())
	    {
	        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;
}