#include <bits/stdc++.h>
using namespace std;
const int maxn = 500005;
int n, m, a[maxn], b[maxn];
vector <int> v[maxn], tura;
int br[maxn], bio1[maxn];
unordered_map <int, int> bio2[maxn];
vector <int> s[maxn];
vector <int> ans[maxn];
int maxi = 0;
void eulers_tour (int x){
while (br[x] < v[x].size()){
int y = v[x][br[x]];
br[x]++;
if (bio1[y] == 0 and bio2[x][y] == 0){
bio2[x][y] = 1;
bio2[y][x] = 1;
eulers_tour(y);
}
}
bio1[x] = 1;
tura.push_back(x);
}
void solve (int poc, int kraj, int brojac){
maxi = max(maxi, brojac);
for (int i = poc; i <= kraj; i++){
int x = tura[i];
ans[brojac].push_back(x);
while (br[x] < s[x].size() and s[x][br[x]] <= kraj) br[x]++;
br[x]--;
if (s[x][br[x]] > i){
int novi = s[x][br[x]];
solve(i + 1, novi, maxi + 1);
i = novi;
}
}
}
int main (void){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin >> n >> m;
for (int i = 0; i < m; i++){
cin >> a[i] >> b[i];
v[a[i]].push_back(b[i]);
v[b[i]].push_back(a[i]);
}
eulers_tour(1);
for (int i = 0; i < tura.size() - 1; i++) s[tura[i]].push_back(i), br[tura[i]] = 0;
solve(0, tura.size() - 2, 0);
for (int i = 0; i <= maxi; i++){
for (int j = 0; j < ans[i].size(); j++) cout << ans[i][j] << " ";
cout << "\n";
}
return 0;
}
