#include <bits/stdc++.h>
int N, M;
std::vector <int> ADC[100005];
inline void addEdge(int u, int v) {
    ADC[u].push_back(v);
}

int nctc;
int low[100005], disc[100005], _time;
std::vector <int> ctc[100005];
bool inStack[100005];
std::stack <int> stack;
void DFS(int vertex) {
    disc[vertex] = low[vertex] = ++_time;
    inStack[vertex] = true;
    stack.push(vertex);

    for (auto &it:ADC[vertex]) {
        if (disc[it]) {
            if (inStack[it]) low[vertex] = std::min(low[vertex], low[it]);
        }
        else {
            DFS(it);
            low[vertex] = std::min(low[vertex], low[it]);
        }
    }

    if (low[vertex] == disc[vertex]) {
        while (!stack.empty() && stack.top() != vertex) {
            ctc[nctc].push_back(stack.top());
            inStack[stack.top()] = false;
            stack.pop();
        }
            ctc[nctc].push_back(stack.top());
            inStack[stack.top()] = false;
            stack.pop();
        ++ nctc;
    }
}

std::ifstream input (std::string("ctc")+".in");
std::ofstream output(std::string("ctc")+".out");

int main()
{
    input >> N >> M;
    for (int i=1, u, v; i<=M; ++i) input >> u >> v, addEdge(u, v);
    for (int i=1; i<=N; ++i)
        if (!disc[i]) DFS(i);
    output << nctc << '\n';
    for (int i=0; i<nctc; ++i, output << '\n')
        for (auto &it:ctc[i])
            output << it << ' ';

    return 0;
}