#include <stdio.h>
#include <algorithm>
#include <vector>
#include <stack>
#define nmax 100010
using namespace std;

int n,m,x,y,rang[nmax];
vector <int> g[nmax],sol;
stack <int> st;

int main() {
	freopen("ciclueuler.in","r",stdin);
	freopen("ciclueuler.out","w",stdout);
	scanf("%d %d",&n,&m);
	for (int i=1;i<=m;i++) {
		scanf("%d %d",&x,&y); g[x].push_back(y); g[y].push_back(x); rang[x]++; rang[y]++;
	}
	for (int i=1;i<=n;i++)
	    if (rang[i]%2==1) { puts("-1"); return 0; }
	st.push(1);
	while (!st.empty()) {
		x=st.top(); 
		if (g[x].size()==0) {
			sol.push_back(x); st.pop(); continue;
		}
		int y=g[x][g[x].size()-1]; 
		st.push(y); g[x].pop_back();
		g[y].erase(find(g[y].begin(),g[y].end(),x));
		
	}
	for (int i=0;i<sol.size();i++) printf("%d ",sol[i]);
	return 0;
}