#include <cstdio>
#include <cstdlib>
#include <vector>
#include <algorithm>
using namespace std;

const int nmax = 100010;

int n, m, x, y, topsort[nmax];
vector<int> g[nmax], gt[nmax];
vector<int> crtctc;
vector<vector<int> > ctc;
bool used[nmax];

void dfp(int node)
{
    used[node] = 1;
    for (int vec : g[node])
    {
        if (used[vec])
            continue;
        dfp(vec);
    }
    topsort[++topsort[0]] = node;
}

void dfm(int node)
{
    used[node] = 0;
    crtctc.push_back(node);

    for (int vec : gt[node])
    {
        if (!used[vec])
            continue;
        dfm(vec);
    }
}

int main()
{
    freopen("in", "r", stdin);

    scanf("%i %i", &n, &m);
    for (int i = 1; i <= m; ++ i)
    {
        scanf("%i %i", &x, &y);
        g[x].push_back(y);
        gt[y].push_back(x);
    }

    for (int i = 1; i <= n; ++ i)
        if (!used[i])
            dfp(i);

    reverse(topsort + 1, topsort + topsort[0] + 1);

    for (int i = 1; i <= n; ++ i)
        if (used[topsort[i]])
        {
            crtctc.clear();
            dfm(topsort[i]);
            ctc.push_back(crtctc);
        }

    printf("%i\n", ctc.size());
    for (int i = 0; i < ctc.size(); ++ i, printf("\n"))
        for (int j = 0; j < ctc[i].size(); ++ j)
            printf("%i ", ctc[i][j]);
}