#include <bits/stdc++.h>
#define _rep(i, x, y) for(int i = x; i <= y; ++i)
#define _req(i, x, y) for(int i = x; i >= y; --i)
#define fi first
#define se second
#define pb push_back
#define mst(f, i) memset(f, i, sizeof f)
#define multitest() int T; read(T); for(int tCase = 1; tCase <= T; ++tCase)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
namespace fastio{
    template<typename T> inline void read(T &t){
        T x = 0, f = 1;
        char c = getchar();
        while(!isdigit(c)){
            if(c == '-') f = -f;
            c = getchar();
        }
        while(isdigit(c)) x = x * 10 + c - '0', c = getchar();
        t = x * f;
    }
    template<typename T, typename ... Args> inline void read(T &t, Args &...args){
        read(t), read(args...);
    }
}
using namespace fastio;
const int N = 5e5 + 5;
int n, m;
vector<pii> G[N];
int id, num, dfn[N], low[N], scc[N];
int top, st[N];
bool vis[N];
vector<int> v[N];
void tarjan(int u, int fa){
    dfn[u] = low[u] = ++id, st[++top] = u;
    for(auto &[v, i] : G[u]){
        if(i == fa) continue;
        if(!dfn[v]){
            tarjan(v, i);
            low[u] = min(low[u], low[v]);
        }else low[u] = min(low[u], dfn[v]);
    }
    if(low[u] == dfn[u]){
        num++;
        for(int x = 0; x != u; top--){
            x = st[top], vis[x] = 0, v[num].pb(x);
        }
    }
}
int main(){
    read(n, m);
    _rep(i, 1, m){
        int u, v; read(u, v), u++, v++;
        G[u].pb({v, i}), G[v].pb({u, i});
    }    
    _rep(i, 1, n) if(!dfn[i]) tarjan(i, 0);
    printf("%d\n", num);
    _req(i, num, 1){
        printf("%d ", v[i].size());
        for(auto &j : v[i]) printf("%d ", j - 1);
        puts("");
    }
    return 0;
}