#include <stdio.h>
#include <iostream>
#include <cstring>
#include <stdlib.h>
#include <time.h>
#include <bitset>
#include <string>
#include <vector>
#include <math.h>
#include <stack>
#include <queue>
#include <list>
#include <set>
#include <limits.h>
#include <algorithm>
#include <deque>
#define nmax 100010
using namespace std;
int n,m,x,y,i,grad[nmax];
vector <int> g[nmax],sol;
stack <int> stiva;
int main(){
freopen("ciclueuler.in","r",stdin);
freopen("ciclueuler.out","w",stdout);
scanf("%d%d",&n,&m);
for (i=1;i<=m;i++){
    scanf("%d%d",&x,&y);
    grad[x]++; grad[y]++;
    g[x].push_back(y); g[y].push_back(x);
}
for (i=1;i<=n;i++)
    if (grad[i]%2==1) { printf("-1"); return 0; }
stiva.push(1);
while (!stiva.empty()){
    x=stiva.top();
    if (g[x].empty()){
        sol.push_back(x);
        stiva.pop();
    } else
    {
        y=g[x][g[x].size()-1]; g[x].pop_back();
        stiva.push(y);
        g[y].erase(find(g[y].begin(),g[y].end(),x));
    }
}
for (i=0;i<sol.size();i++) printf("%d ",sol[i]);
return 0;
}