#include <bits/stdc++.h>
using namespace std;

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define MP make_pair
#define PB push_back
#define F first
#define S second
#define FILL(a, b) memset(a, b, sizeof(a))

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;

const int N = 200447;
VI g[N];
bool used[N];

void dfs(int v, bool b)
{
	if (b) cout << v + 1 << ' ';
	used[v] = 1;
	for (auto to : g[v])
		if (!used[to])
			dfs(to, !b);
	if (!b) cout << v + 1 << ' ';
	
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	int n, m;
	cin >> n >> m;
	FOR (i, 0, m)
	{
		int a, b;
		cin >> a >> b;
		a--, b--;
		g[a].PB(b);
		g[b].PB(a);
	}
	dfs(0, 1);
	cout << '\n';
	
	
	
	return 0;
}