#include <fstream>
#include <vector>

#define maxn 100001
#define vint vector<int>::iterator

using namespace std;

ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

vector<int> G[maxn],CC[maxn];
int lowlink[maxn],index[maxn],current,stack[maxn],n,m,a,b,t,nr;
bool is_in_stack[maxn];

void Tarjan (int x)
{
    index[x] = ++current;
    lowlink[x] = index[x];
    is_in_stack[x] = 1;
    stack [++t] = x;

    for (vint it = G[x].begin(); it != G[x].end(); ++it)
    {
        if (!index[*it])
        {
            Tarjan (*it);
            lowlink[x] = min (lowlink[x],lowlink[*it]);
        }
        else if (is_in_stack[*it])
        {
            lowlink[x] = min (lowlink[x],lowlink[*it]);
        }
    }

    if (lowlink[x] == index[x])
    {
        ++nr;
        while ( stack[t] != x)
        {
            CC[nr].push_back (stack[t]);
            is_in_stack[stack[t]] = 0;
            --t;
        }
        CC[nr].push_back (x);
        is_in_stack[x] = 0;
        --t;
    }
}

int main()
{
    fin>>n>>m;

    for (int i=1; i<=m; ++i)
    {
        fin>>a>>b;
        G[a].push_back (b);
    }

    for (int i=1; i<=n; ++i)
    {
        if (!index[i]) Tarjan(i);
    }

    fout<<nr<<"\n";

    for (int i=1; i<=nr; ++i)
    {
        for (vint it = CC[i].begin(); it != CC[i].end(); ++it)
        {
            fout<<*it<<" ";
        }
        fout<<"\n";
    }
}