#include <bits/stdc++.h>

using namespace std;

const int NMAX = 1e5 + 5;

vector<int> a[NMAX];
vector<int> a_t[NMAX];
vector<int> sol[NMAX];
stack<int> stiva;

int viz[NMAX], viz_t[NMAX];

int nc;

void dfs(int nod) {
    viz[nod] = 1;
    for (int fiu : a[nod]) {
        if (viz[fiu] == 0)
            dfs(fiu);
    }
    stiva.push(nod);
}

void dfs_t(int nod) {
    viz_t[nod] = 1;
    sol[nc].push_back(nod);
    for (int fiu : a_t[nod]) {
        if (viz_t[fiu] == 0)
            dfs_t(fiu);
    }
}

int main() {

    freopen ("ctc.in", "r", stdin);
    freopen ("ctc.out", "w", stdout);

    int n, m, i, x, n1, n2;

    scanf ("%d%d", &n, &m);

    for (i = 1; i <= m; i++) {
        scanf ("%d%d", &n1, &n2);
        a[n1].push_back(n2);
        a_t[n2].push_back(n1);
    }

    for (i = 1; i <= n; i++) {
        if (viz[i] == 0) {
            dfs(i);
        }
    }

    while (!stiva.empty()) {
        x = stiva.top();
       // cout << x << " ";
        stiva.pop();
        if (viz_t[x] == 0) {
            nc++;
            dfs_t(x);
        }

    }

    printf ("%d\n", nc);
    for (i = 1; i <= nc; i++) {
        for (int x : sol[i])
            printf ("%d ", x);
        printf ("\n");
    }

    return 0;
}