#include <bits/stdc++.h>

using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");
const int NMAX = 1e5+5;
vector<int> v[NMAX], vt[NMAX], sol[NMAX];
bool viz[NMAX];
stack <int> comp;
int nr;

void dfp(int x)
{
    viz[x] = 1;
    for (auto it: v[x])
        if (!viz[it])
            dfp(it);
    comp.push(x);
}

void dfm(int x)
{
    sol[nr].push_back(x);
    viz[x] = 1;
    for (auto it: vt[x])
        if (!viz[it])
            dfm(it);
}

int main()
{
    int n,m;
    in >> n >> m;
    for (int i = 1; i<=m; i++)
    {
        int x,y;
        in >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for (int i = 1; i<=n; i++)
        if (!viz[i])
            dfp(i);
    memset(viz,0,sizeof(viz));
    while (!comp.empty())
    {
        int now = comp.top();
        if (!viz[now])
        {
            nr++;
            dfm(now);
        }
        comp.pop();
    }
    out << nr << "\n";
    for (int i = 1; i<=nr; i++)
    {
        for (auto it: sol[i])
            out << it << " ";
        out << "\n";
    }
}