#include <bits/stdc++.h>
using namespace std;
void setup()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
int n, m, a, b;
bool check[500000], mark[500000];
vector<pair<int, int>> g[500000];
vector<int> v;
inline void DFS(int node)
{
if (check[node])
{
while (!v.empty() && check[node])
{
cout << v.back() + 1 << " ";
check[v.back()] = false;
v.pop_back();
}
cout << "\n";
}
while (!g[node].empty())
{
a = g[node].back().first;
b = g[node].back().second;
g[node].pop_back();
if (!mark[b])
{
mark[b] = check[node] = true;
v.push_back(node);
DFS(a);
}
}
}
int main()
{
setup();
cin >> n >> m;
for (int i = 0; i < m; ++i)
{
cin >> a >> b;
g[a - 1].push_back({b - 1, i});
g[b - 1].push_back({a - 1, i});
}
DFS(0);
return 0;
}
