#include <cstdio>
#include <algorithm>
#include <iostream>
#include <vector>
#include <queue>
#include <stack>

using namespace std;

int N, M;
vector <vector <int> > graph;
vector <int> degree, ans;
stack <int> last_node;

bool ConnectedAndEvenDegree() {
	queue <int> que;
	vector <bool> visited(N + 1);
	if (degree[1] % 2 == 1) {
		return false;
	}
	int left_nodes = N - 1;
	que.push(1);
	visited[1] = true;
	while (!que.empty()) {
		int iam = que.front();
		que.pop();
		for (auto to: graph[iam]) {
			if (!visited[to]) {
				visited[to] = true;
				--left_nodes;
				que.push(to);
				if (degree[to] % 2 == 1) {
					return false;
				}
			}
		}
	}
	return (left_nodes == 0);
}

void DFS(int iam) {
	while (true) {
		if (graph[iam].empty()) {
			break;
		}
		int to = graph[iam][0];
		last_node.push(iam);
		graph[iam].erase(graph[iam].begin());
		for (auto w = graph[to].begin(); w != graph[to].end(); ++w) {
			if (*w == iam) {
				graph[to].erase(w);
				break;
			}
		}
		
		iam = to;
	}
}

void FindCicles() {
	int iam = 1;
	do {
		DFS(iam);
		iam = last_node.top();
		last_node.pop();
		ans.push_back(iam);
	} while (!last_node.empty());
}



int main() {
#ifdef INFOARENA
	freopen("ciclueuler.in", "r", stdin);
	freopen("ciclueuler.out", "w", stdout);
#else
	freopen("/Users/duxar/Workplace/Xcode Projects/Selectie/Selectie/input", "r", stdin);
#endif
	
	int i, x, y;
	
	scanf("%d %d", &N, &M);
	graph.resize(N + 1);
	degree.resize(N + 1);
	for (i = 1; i <= M; ++i) {
		scanf("%d %d", &x, &y);
		graph[x].push_back(y);
		graph[y].push_back(x);
		++degree[x];
		++degree[y];
	}
	
	if (!ConnectedAndEvenDegree()) {
		printf("-1\n");
		return 0;
	}
	
	FindCicles();
	
	for (auto iam: ans) {
		printf("%d ", iam);
	}
	printf("\n");
	
	
	
	return 0;
}