#include <bits/stdc++.h>
using namespace std;
#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define SZ(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for (int i=(a);i>=(b);--i)
typedef pair<int,int> ii;
const int mxN = 5e5+5;
const int mxM = 5e5+5;
int N, M;
struct Edge { int v, i, n; } el[2*mxM];
int al[mxN];
bool vis[mxN];
bool used[mxM];
vector<int> cyc;
void dfs(int u) {
if (vis[u]) {
int v;
do {
v = cyc.back();
cout << v << ' ';
cyc.pop_back();
vis[v] = 0;
} while (v != u);
cout << '\n';
}
cyc.push_back(u);
vis[u] = 1;
while (al[u] > 0) {
Edge e = el[al[u]];
al[u] = e.n;
if (!used[e.i]) {
used[e.i] = 1;
dfs(e.v);
break;
}
}
}
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> N >> M;
FOR(i,1,M){
int U, V; cin >> U >> V;
el[2*i-1] = (Edge){V,i,al[U]};
el[2*i] = (Edge){U,i,al[V]};
al[U] = 2*i-1;
al[V] = 2*i;
}
FOR(i,1,N){
dfs(i);
while (SZ(cyc)) {
vis[cyc.back()] = 0;
cyc.pop_back();
}
}
}
