#include <iostream>
#include <fstream>
#include <stack>
#include <vector>

#define nmax 100005
using namespace std;

vector<int> g[nmax];
vector<int> sol;
int n,m,d;
stack<int> s;

void read()
{
    int x,y;
    scanf("%d %d",&n,&m);
    for(int i=0;i<m;i++)
    {
        scanf("%d %d",&x,&y);
        g[x].push_back(y);
        g[y].push_back(x);
    }
}

void delete_nod(int x,int y)
{
    for(int i=0;i<g[y].size();i++)
        if(g[y][i]==x)
            {g[y].erase(g[y].begin()+i);
            return;}
}
void euler()
{
    s.push(1);
    while(!s.empty())
    {
        int aux=s.top();
        if(!g[aux].empty())
        {
            int k=g[aux][0];
            d++;
            g[aux].erase(g[aux].begin());
            delete_nod(aux,k);
            s.push(k);
            continue;
        }
        sol.push_back(aux);
        s.pop();
    }

    if(d==m)
        for(int i=sol.size()-1;i>=0;i--)
            printf("%d ",sol[i]);
    else printf("-1\n");
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    read();
    euler();
    return 0;
}