#include <cstdio>
#include <algorithm>
#include <vector>
#include <stack>
#define nmax 100002
using namespace std;

FILE *f1=fopen("ciclueuler.in","r"),*f2=fopen("ciclueuler.out","w");

vector <int> g[nmax],sol;
stack  <int> st;

int n,m,i;

void sterge(int x, int y)
{
    g[x][0]=g[x][g[x].size()-1];
    g[x].pop_back();
    g[y].erase(find(g[y].begin(),g[y].end(),x));
}

void euler()
{
    int nod;

    for(nod=1;nod<=n;nod++)
        if(g[nod].size()&1)return;

    st.push(1);
    while(!st.empty())
    {
        nod=st.top();
        if(g[nod].size()>0)
        {
            st.push(g[nod].front());
            sterge(nod,g[nod].front());
        }
        else
        {
            sol.push_back(nod);
            st.pop();
        }
    }
}
int main()
{
    fscanf(f1,"%d%d",&n,&m);
    for(;m--;){int x,y;fscanf(f1,"%d%d",&x,&y);g[x].push_back(y);g[y].push_back(x);}
    euler();
    if(!sol.size())fprintf(f2,"-1");
    else
    for(i=1;i<sol.size();i++)
    {
        fprintf(f2,"%d ",sol[i]);
    }
    fclose(f1);
    fclose(f2);
    return 0;
}