#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;

const int max1 = 5e5;

int n, m;
vector <int> edge[max1 + 5];

int dfn[max1 + 5], low[max1 + 5], dfs_clock;
int s[max1 + 5], top;

int cnt;
vector <int> ans[max1 + 5];

void Tarjan ( int now, int fa )
{
    dfn[now] = low[now] = ++dfs_clock;
    s[++top] = now;

    bool is_first = true;
    for ( auto v : edge[now] )
    {
        if ( is_first && v == fa )
            { is_first = false; continue; }
        
        if ( !dfn[v] )
        {
            Tarjan(v, now);
            low[now] = min(low[now], low[v]);
        }
        else
        {
            low[now] = min(low[now], dfn[v]);
        }
    }

    if ( dfn[now] == low[now] )
    {
        int x; ++cnt;
        do
        {
            x = s[top--];
            ans[cnt].push_back(x);
        } while ( x != now );
    }
    return;
}

int main ()
{
    scanf("%d%d", &n, &m);
    for ( int i = 1, u, v; i <= m; i ++ )
    {
        scanf("%d%d", &u, &v);
        ++u; ++v;
        edge[u].push_back(v);
        edge[v].push_back(u);
    }

    for ( int i = 1; i <= n; i ++ )
        if ( !dfn[i] )
            Tarjan(i, 0);
    
    printf("%d\n", cnt);
    for ( int i = 1; i <= cnt; i ++ )
    {
        printf("%lu ", ans[i].size());
        for ( auto v : ans[i] )
            printf("%d ", v - 1);
        printf("\n");
    }

    return 0;
}