#include <cstdio>
#include <vector>
#define DIMBUFF 100000
using namespace std;
FILE * fin = fopen ("ciclueuler.in", "r");
FILE *fout = fopen ("ciclueuler.out", "w");
vector<int> v[100001],sol;
int a[500001],b[500001],n,m,i;
bool d[500001];
char buff[DIMBUFF];
int pp;

int numar() {
    int val = 0;
    while (!(buff[pp] >= '0' && buff[pp] <= '9')) {
        pp++;
        if (pp == DIMBUFF) {
            fread(buff, 1, DIMBUFF, fin);
            pp=0;
        }
    }
    while (buff[pp] >= '0' && buff[pp] <= '9') {
        val = val*10 + buff[pp] - '0';
        pp++;
        if (pp == DIMBUFF) {
            fread(buff, 1, DIMBUFF, fin);
            pp=0;
        }
    }
    return val;
}
inline void dfs(int nod)
{
    for(vector<int>::iterator it=v[nod].begin();it!=v[nod].end();it++)
        if(d[*it]==0)
            d[*it]=1,dfs(a[*it]+b[*it]-nod);
    sol.push_back(nod);
}
int main()
{
    fread(buff, 1, DIMBUFF, fin);
    n=numar();m=numar();
    for(i=1;i<=m;i++)
    {
        a[i]=numar();b[i]=numar();
        v[a[i]].push_back(i);
        v[b[i]].push_back(i);
    }
    for(i=1;i<=n;i++)
        if(v[i].size()&1)
        {
            fprintf(fout,"-1");
            return 0;
        }
    dfs(1);
    for(vector<int>::iterator it=sol.end()-1;it!=sol.begin();it--)
		fprintf(fout,"%d ",*it);
    return 0;
}