code = r"""
# distutils: language=c++
# distutils: include_dirs=[/home/contestant/.local/lib/python3.8/site-packages/numpy/core/include,/opt/atcoder-stl]
# cython: boundscheck=False
# cython: wraparound=False
from libcpp cimport bool
from libcpp.string cimport string
from libcpp.vector cimport vector

cdef extern from "<atcoder/dsu>" namespace "atcoder":
    cpdef cppclass dsu:
        dsu(int n)
        int merge(int a, int b)
        bool same(int a, int b)
        int leader(int a)
        int size(int a)
        vector[vector[int]] groups()
cdef class dsu_:
    cdef dsu *ptr
    def __cinit__(self, int n): self.ptr = new dsu(n)
    def __dealloc__(self): del self.ptr
    cpdef int merge(self,a,b): return self.ptr.merge(a,b)
    cpdef bool same(self,a,b): return self.ptr.same(a,b)
    cpdef int leader(self,a): return self.ptr.leader(a)
    cpdef int size(self,a): return self.ptr.size(a)
    cpdef vector[vector[int]] groups(self): return self.ptr.groups()

cdef extern from "<atcoder/fenwicktree>" namespace "atcoder":
    cdef cppclass fenwick_tree[T]:
        fenwick_tree(int n)
        void add(int p, T x)
        T sum(int l, int r)
cdef class fenwick_tree_:
    cdef fenwick_tree[int] *ptr
    def __cinit__(self, int n): self.ptr = new fenwick_tree[int](n)  
    def __dealloc__(self): del self.ptr
    cpdef void add(self, int p, long x): self.ptr.add(p, x)
    cpdef long sum(self, int l, int r): return self.ptr.sum(l, r)

cdef extern from "<atcoder/string>" namespace "atcoder":
    vector[int] suffix_array(vector[int] s, int upper)
    vector[int] suffix_array(vector[long] s)
    vector[int] suffix_array(string s)
    vector[int] lcp_array(vector[long] s, vector[int] sa)
    vector[int] lcp_array(string s, vector[int] sa)
    vector[int] z_algorithm(vector[long] s)
    vector[int] z_algorithm(string s)
cpdef vector[int] suffix_array_u(vector[int] s, int upper): return suffix_array(s, upper)
cpdef vector[int] suffix_array_l(vector[long] s): return suffix_array(s)
cpdef vector[int] suffix_array_s(string s): return suffix_array(s)
cpdef vector[int] lcp_array_l(vector[long] s, vector[int] sa): return lcp_array(s, sa)
cpdef vector[int] lcp_array_s(string s, vector[int] sa): return lcp_array(s, sa)
cpdef vector[int] z_algorithm_l(vector[long] s): return z_algorithm(s)
cpdef vector[int] z_algorithm_s(string s): return z_algorithm(s)

cdef extern from "<atcoder/maxflow>" namespace "atcoder":
    cdef cppclass mf_graph[Cap]:
        mf_graph(int n)
        int add_edge(int frm, int to, Cap cap)
        Cap flow(int s, int t)
        Cap flow(int s, int t, Cap flow_limit)
        vector[bool] min_cut(int s)
        cppclass edge:
            int frm "from", to
            Cap cap, flow
            edge(edge &e)
        edge get_edge(int i)
        vector[edge] edges()
        void change_edge(int i, Cap new_cap, Cap new_flow)
cdef class mf_graph_:
    cdef mf_graph[int] *ptr
    def __cinit__(self, int n): self.ptr = new mf_graph[int](n)  
    def __dealloc__(self): del self.ptr
    cpdef int add_edge(self, int frm, int to, int cap): return self.ptr.add_edge(frm, to, cap)
    cpdef int flow(self, int s, int t): return self.ptr.flow(s, t)
    cpdef int flow_limit(self, int s, int t, int flow_limit): return self.ptr.flow(s, t, flow_limit)
    cpdef vector[bool] min_cut(self, int s): return self.ptr.min_cut(s)
    cpdef vector[int] get_edge(self, int i):
        cdef mf_graph[int].edge *e = new mf_graph[int].edge(self.ptr.get_edge(i))
        cdef vector[int] *ret_e = new vector[int]()        
        ret_e.push_back(e.frm)
        ret_e.push_back(e.to)
        ret_e.push_back(e.cap)
        ret_e.push_back(e.flow)
        return ret_e[0]
    cpdef vector[vector[int]] edges(self):
        cdef vector[mf_graph[int].edge] es = self.ptr.edges()
        cdef vector[vector[int]] *ret_es = new vector[vector[int]](es.size())
        for i in range(es.size()):
            ret_es.at(i).push_back(es.at(i).frm)
            ret_es.at(i).push_back(es.at(i).to)
            ret_es.at(i).push_back(es.at(i).cap)
            ret_es.at(i).push_back(es.at(i).flow)
        return ret_es[0]
    cpdef void change_edge(self, int i, int new_cap, int new_flow): self.ptr.change_edge(i, new_cap, new_flow)

cdef extern from *:
    ctypedef int MOD "998244353"
    ctypedef long long ll "long long"
cdef extern from "<atcoder/convolution>" namespace "atcoder":
    vector[int] convolution[m](vector[int] a, vector[int] b)
    vector[ll] convolution_ll(vector[ll] a, vector[ll] b)
cpdef vector[int] convolution_(vector[int] a, vector[int] b): return convolution[MOD](a, b)
cpdef vector[ll] convolution_ll_(vector[ll] a, vector[ll] b): return convolution_ll(a, b)

cdef extern from "<atcoder/scc>" namespace "atcoder":
    cdef cppclass scc_graph:
        scc_graph(int n)
        void add_edge(int fr, int to)
        vector[vector[int]] scc()
cdef class scc_graph_:
    cdef scc_graph *ptr
    def __cinit__(self, int n): self.ptr = new scc_graph(n)  
    def __dealloc__(self): del self.ptr
    cpdef void add_edge(self, int fr, int to): self.ptr.add_edge(fr, to)
    cpdef vector[vector[int]] scc(self): return self.ptr.scc()
"""

import os
try:
    from atcoder import *
except:
    open('atcoder.pyx', 'w').write(code)
    os.system('cythonize -i -3 -b atcoder.pyx')

N,M=map(int,input().split())
AB=[list(map(int,input().split())) for i in range(M)]
g=scc_graph_(N)
for a,b in AB:
    g.add_edge(a,b)
r=g.scc()
print(len(r))
for l in r:
    print(len(l),*l)

Measured memory_bytes: 203564