#include <cstdio>
#include <vector>
using namespace std;
const int NMAX = 100000;
vector <int> g[NMAX + 5], gtr[NMAX + 5], rez[NMAX + 5];
int viz[NMAX + 5], sol[NMAX + 5], ans = 0;
void dfs(int x)
{
    int y; viz[x] = 1;
    for (int i = 0; i < g[x].size(); ++i)
    {
        y = g[x][i];
        if (viz[y] == 0)
            dfs(y);
    }
    sol[++sol[0]] = x;
}
void dfs2(int x)
{
    int y; viz[x] = ans;
    rez[ans].push_back(x);
    for (int i = 0; i < gtr[x].size(); ++i)
    {
        y = gtr[x][i];
        if (viz[y] == 0)
            dfs2(y);
    }
}
int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    int n, m, a, b;
    scanf("%d %d", &n, &m);
    for (int i = 1; i <= m; ++i)
    {
        scanf("%d %d", &a, &b);
        g[a].push_back(b);
        gtr[b].push_back(a);
    }
    for (int i = 1; i <= n; ++i)
        if (viz[i] == 0)
            dfs(i);
    for (int i = 1; i <= n; ++i)
        viz[i] = 0;
    for (int i = n; i > 0; --i)
        if (viz[sol[i]] == 0)
            ++ans, dfs2(sol[i]);
    printf("%d\n", ans);
    for (int i = 1; i <= ans; ++i)
    {
        for (int j = 0; j < rez[i].size(); ++j)
            printf("%d ", rez[i][j]);
        printf("\n");
    }
    return 0;
}