#include <cstdio>
#include <vector>
#include <algorithm>
#include <stack>
#include <queue>

using namespace std;
const int NMAX=100000;
const int MMAX=500000;
vector<int> g[NMAX+5];
stack<int> st;
int nod,other,n,m;
bool euler()
{
    return 1;
}
void solve()
{
    int i,j;
    while(g[nod].size())
    {
        st.push(nod);
        other=g[nod][g[nod].size()-1];
        g[nod].pop_back();
        vector<int>::iterator it;
        it=find(g[other].begin(),g[other].end(),nod);
        g[other].erase(it);
        nod=other;
    }
    while(!st.empty())
    {
        printf("%d ", st.top());
        if(!g[st.top()].empty())
        {
            nod=st.top();
            solve();
            break;
        }
        else
        {
            st.pop();
        }
    }
}

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    int i,j,u,v;
    scanf("%d%d", &n,&m);
    for(i=1;i<=m;i++)
    {
        scanf("%d%d", &u,&v);
        g[u].push_back(v);
        g[v].push_back(u);
    }
    nod=1;
    if(euler())
        solve();
    else
        printf("-1\n");
    return 0;
}