#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#define Nmax 100002
using namespace std;
int n, m, i, j, d[Nmax], v[Nmax], used[Nmax], c, nexti, nre;
vector < int > V[Nmax], C[Nmax];
bool viz[Nmax];
struct edge
{
    int x;
    int y;
} scc[Nmax];
void read()
{
    int x, y;
    freopen("biconex.in", "r", stdin);
    freopen("biconex.out", "w", stdout);
    scanf("%d %d", &n, &m);
    for (i = 1; i <= m; ++ i)
    {
        scanf("%d %d", &x, &y);
        V[x].push_back(y);
        V[y].push_back(x);
    }
}
void bcc(int x, int y)
{
    edge e;
    do
    {
        e = scc[nre--];
        if (used[e.x] != c)
        {
            C[c].push_back(e.x);
            used[e.x] = c;
        }
        if (used[e.y] != c)
        {
            C[c].push_back(e.y);
            used[e.y] = c;
        }
        if (e.x == x && e.y == y)
            break;

    } while (nre > 0);
    ++ c;
}
void dfs(int x)
{
    int i, l = V[x].size(), nrs = 0;
    viz[x] = 1;
    d[x] = v[x] = ++ nexti;
    for (i = 0; i < l; ++ i)
        if (!viz[V[x][i]])
        {
            scc[++ nre].x = x;
            scc[nre].y = V[x][i];
            ++ nrs;
            dfs(V[x][i]);
            d[x] = min(d[x], d[V[x][i]]);
            if (d[V[x][i]] >= v[x])
                bcc(x, V[x][i]);
        }
        else d[x] = min(d[x], v[V[x][i]]);
}
void solve()
{
    for (i = 1; i <= n; ++ i)
        used[i] = -1;
    for (i = 1; i <= n; ++ i)
        if (!viz[i])
        {
            viz[i] = 1;
            nre = 0;
            dfs(i);
        }
}
void write()
{
    int l;
    printf("%d\n", c);
    for (i = 0; i < c; ++ i)
    {
        l = C[i].size();
        for (j = 0; j < l; ++ j)
            printf("%d ", C[i][j]);
        printf("\n");
    }
}
int main()
{
    read();
    solve();
    write();
    return 0;
}