#include <bits/stdc++.h>

const int MAX_N = 100000;

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, m, ctc;
int visited[MAX_N + 5];

vector<int>neighbors[MAX_N + 5], neighborsT[MAX_N + 5], L, vertices[MAX_N + 5];

void dfs(int u) {
    visited[u] = 1;
    for(int v : neighbors[u])
        if(!visited[v])
            dfs(v);

    L.push_back(u);
}

void dfsT(int u) {
    visited[u] = 1;
    for(int v : neighborsT[u])
        if(!visited[v])
            dfsT(v);

    vertices[ctc].push_back(u);
}

int main() {
    fin >> n >> m;
    for(int i = 1; i <= m; i++) {
        int x, y;
        fin >> x >> y;
        neighbors[x].push_back(y);
        neighborsT[y].push_back(x);
    }

    for(int i = 1; i <= n; i++)
        if(!visited[i])
            dfs(i);

    for(int u : L)
        visited[u] = 0;

    reverse(L.begin(), L.end());

    for(int u : L)
        if(!visited[u]) {
            ctc++;
            dfsT(u);
        }

    fout << ctc << '\n';
    for(int i = 1; i <= ctc; i++) {
        for(int u : vertices[i])
            fout << u << ' ';
        fout << '\n';
    }
    return 0;
}