#include<bits/stdc++.h>
using namespace std;
#define task "a"
#define se second
#define fi first
#define ll long long
#define ii pair<ll, ll>
const long mxN = 5e5 + 7;
bool vis[mxN], dd[mxN];
int n, m;
vector<ii> w[mxN];
void Euler_Cycle(int cur)
{
vector<int> v;
while (1)
{
if (vis[cur])
{
while (1)
{
int j = v.back();
v.pop_back();
vis[j] = 0;
cout << j << " ";
if (j == cur)
break;
}
cout << '\n';
}
v.push_back(cur);
vis[cur] = 1;
while (w[cur].size() && dd[w[cur].back().se])
w[cur].pop_back();
if (w[cur].empty())
return;
dd[w[cur].back().se] = 1;
cur = w[cur].back().fi;
}
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
//freopen(task".INP", "r", stdin);
//freopen(task".OUT", "w", stdout);
cin >> n >> m;
for (int i = 1; i <= m; i++)
{
int u, v;
cin >> u >> v;
w[u].push_back({v, i});
w[v].push_back({u, i});
}
for (int i = 1; i <= n; i++)
Euler_Cycle(i);
}
