#include<cstdio>
#include<vector>
#include <cassert>
#include<utility>
using namespace std;
#define pb push_back
#define sz(a) (int)(a.size())
constexpr int maxn = 5e5+10;
vector<pair<int,int>> g[maxn];
vector<int> st;
bool mark[maxn], mark_edge[maxn];
int rd() {
bool minus = false;
int result = 0;
char ch;
ch = getchar();
while (true) {
if (ch == '-') break;
if (ch >= '0' && ch <= '9') break;
ch = getchar();
}
if (ch == '-') minus = true; else result = ch-'0';
while (true) {
ch = getchar();
if (ch < '0' || ch > '9') break;
result = result*10 + (ch - '0');
}
if (minus)
return -result;
else
return result;
}
void dfs(int i) {
st.pb(i);
while(1) {
int u = st.back();
mark[u] = 1;
while(g[u].size() && mark_edge[g[u].back().second])
g[u].pop_back();
if(!sz(g[u])) break;
int v = g[u].back().first;
mark_edge[g[u].back().second] = 1;
g[u].pop_back();
if(mark[v]) {
printf("%d", v);
while(st.size() && st.back() != v) {
printf(" %d", st.back());
mark[st.back()] = 0;
st.pop_back();
}
printf("\n");
}
else st.pb(v);
}
mark[i] = 0;
st.clear();
}
int main() {
int n = rd(), m = rd(); // scanf("%d %d", &n, &m);
for(int i = 0, a, b; i < m; i++)
a=rd(), b=rd(), g[a].pb({b, i}), g[b].pb({a, i});
// scanf("%d %d", &a, &b), g[a].pb({b, i}), g[b].pb({a, i});
for(int i = 1; i <= n; i++)
if(sz(g[i])) dfs(i);
}
