#include<cstdio>
#include<vector>
#define maxn 100001
#define maxm 500001
using namespace std;
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)
{	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[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) {printf("-1\n"); return 0;}
	dfs(1);
	for(vector<int> :: iterator it=sol.end()-1;it!=sol.begin();--it)
		printf("%d ",*it);	//g<<*it<<" ";
	printf("\n"); return 0;
}