#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
const int N = 500000;
const int M = 500000;
int ij[M], ii[M + 1], qu[N];
vector<int> eh[N];
bool used[M], inqu[N];
void dfs(int i) {
static int z;
while (!eh[i].empty()) {
int h = eh[i].back(); eh[i].pop_back();
if (!used[h]) {
int j = i ^ ij[h];
used[h] = true, dfs(j);
}
}
ii[z++] = i;
}
int main() {
ios_base::sync_with_stdio(false), cin.tie(NULL);
int n, m; cin >> n >> m;
for (int h = 0; h < m; h++) {
int i, j; cin >> i >> j, i--, j--;
ij[h] = i ^ j;
eh[i].push_back(h);
eh[j].push_back(h);
}
dfs(0);
int cnt = 0;
for (int z = 0; z <= m; z++) {
int i = ii[z];
if (!inqu[i])
inqu[qu[cnt++] = i] = true;
else {
cout << i + 1;
for (int j; (j = qu[cnt - 1]) != i; cnt--) {
inqu[j] = false;
cout << ' ' << j + 1;
}
cout << '\n';
}
}
return 0;
}
