#include<cstdio>
#include<fstream>
#include<vector>
#define maxn 100001
#define maxm 500001
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
vector<int> a[maxn],sol;
bool viz[maxm];
int n,m,i,x[maxm],y[maxm];
inline void dfs(int s)
{
	for(vector<int> :: iterator it=a[s].begin();it!=a[s].end();++it)
		if(viz[*it]==0)
			viz[*it]=1,dfs(x[*it]+y[*it]-s);
		sol.push_back(s);
}
int main(void)
{	f>>n>>m;
	for(i=1;i<=m;i++)
	{	f>>x[i]>>y[i];
		a[x[i]].push_back(i);
		a[y[i]].push_back(i);
	}
	for(i=1;i<=n;i++)
		if(a[i].size() & 1) {g<<"-1"; return 0;}
	dfs(1);
	for(vector<int> :: iterator it=sol.end()-1;it!=sol.begin();--it)
		g<<*it<<" ";
	return 0;
}