#include<cstdio>
#include<vector>
#include<stack>
#include<algorithm>
#define maxn 500005
using namespace std;
FILE *f=fopen("ciclueuler.in","r");
FILE *g=fopen("ciclueuler.out","w");
vector <int> v[maxn];
stack <int> stiv;
int n,m,x,y,ok=1;
void euler(){
	stiv.push(1);
	while(stiv.size()>0){
		x=stiv.top();
		if(v[x].size()>0){
			int y=v[x][0];
			stiv.push(y);
			v[x].erase(v[x].begin());
			v[y].erase(find(v[y].begin(),v[y].end(),x));
		}
		else
			fprintf(g,"%d ",x),stiv.pop();
	}
}
int main (){
	fscanf(f,"%d%d",&n,&m);
	for(int i=1;i<=m;i++){
		fscanf(f,"%d%d",&x,&y);
		v[x].push_back(y);
		v[y].push_back(x);
	}
	for(int i=1;i<=n && ok==1;i++){
		if(v[i].size()%2!=0)
			ok=0;
	}
	if(ok)
		euler();
	else
		fprintf(g,"%d ",-1);
	return 0;
}