import copy
import random

adj_list = {}
trans_adj_list = {}
my_list = []


def add_node(node):
    if node not in my_list:
        my_list.append(node)


def add_edge(node1, node2, my_graph):
    temp = []
    if node1 in my_list and node2 in my_list:
        if node1 not in my_graph:
            temp.append(node2)
            my_graph[node1] = temp
        elif node1 in my_graph:
            temp.extend(my_graph[node1])
            temp.append(node2)
            my_graph[node1] = temp


def dfs(my_graph, starting_node):
    stack, result = [starting_node], []
    while stack:
        node = stack.pop()
        if node in result:
            continue
        result.append(node)
        if node in my_graph:
            for n in my_graph[node]:
                stack.append(n)
    return result


def read():
    n, m = [int(x) for x in f.readline().split()]
    for i in range(1, n + 1):
        add_node(i)
    for i in range(m):
        x, y = [int(z) for z in f.readline().split()]
        add_edge(x, y, adj_list)  # graph is oriented
        add_edge(y, x, trans_adj_list)  # transpose graph
    return n, m


def remove_key(my_graph, delete_value):
    if delete_value in my_graph:
        del my_graph[delete_value]
    for edges in my_graph.values():
        copy_edge = copy.deepcopy(edges)
        if delete_value in copy_edge:
            edges.remove(delete_value)


def find_ctc_components():
    ctc = []
    while adj_list:
        nod = random.choice(list(adj_list.keys()))
        result_dfs = dfs(adj_list, nod)
        trans_result_dfs = dfs(trans_adj_list, nod)
        plus_minus = list(set(result_dfs) & set(trans_result_dfs))
        ctc.append(plus_minus)
        for member in plus_minus:
            remove_key(adj_list, member)
            remove_key(trans_adj_list, member)
    # if keys are left in trans_adj_list then they are from ctc
    for nod in trans_adj_list.keys():
        aux = [nod]
        ctc.append(aux)
    return ctc


f = open("ctc.in", "r")
f_out = open("ctc.out", "w")
N, M = read()
my_ctc = find_ctc_components()
f_out.write(str(len(my_ctc)))
f_out.write('\n')
for x in my_ctc:
    f_out.write(" ".join(str(y) for y in x))
    f_out.write('\n')