#include <bits/stdc++.h>
using namespace std;
vector <int> v[100005];
vector <int> a[100005];
stack <int> steck;
int iden[100005], low[100005], k, i, j, ctc, l , n, m, x, y, aux;
bool onstack[100005], viz[100005];
void dfs(int x)
{
    iden[x] = low[x] = ++k;
    steck.push(x);
    onstack[x] = true;
    for(int i = 0; i < v[x].size(); i ++)
    {
        int aux = v[x][i];
        if(viz[aux] == false)
        {
            viz[aux] = true;
            onstack[aux] = true;
            dfs(aux);
        }
        if(low[aux] < low[x] && onstack[aux] == true)low[x] = low[aux];
    }
    if(iden[x] == low[x])
    {
        ctc++;
        while(steck.top() != x)
        {
            aux = steck.top();
            a[ctc].push_back(aux);
            onstack[aux] = false;
            steck.pop();
        }
        aux = steck.top();
        a[ctc].push_back(aux);
        onstack[aux] = false;
        steck.pop();
    }
}
int main()
{
    ifstream f("ctc.in");
    ofstream g("ctc.out");
    f >> n >> m;
    for(i = 1; i <= m; i ++)
    {
        f >> x >> y;
        v[x].push_back(y);
    }
    for(i = 1; i <= n; i ++)
        if(viz[i] == false)k = 0, dfs(i);
    g << ctc << "\n";
    for(i = 1; i <= ctc; i ++)
    {
        for(j = 0; j < a[i].size(); j ++)
            g << a[i][j] << " ";
        g << "\n";
    }
    return 0;
}