#include <bits/stdc++.h>

using namespace std;

constexpr int NMax=100005;

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

int N,M,nSol;
vector<int> G[NMax],T[NMax],sol[NMax];
bool visited[NMax];
stack<int> Stack;

void DFS1(int node)
{
    visited[node]=true;
    for(auto child : G[node])
        if(!visited[child])
            DFS1(child);
    Stack.push(node);
}

void DFS2(int node)
{
    sol[nSol].push_back(node);
    visited[node]=true;
    for(auto child : T[node])
        if(!visited[child])
            DFS2(child);
}

int main()
{
    fin>>N>>M;
    for(int i=1;i<=M;i++)
    {
        int x,y;
        fin>>x>>y;
        G[x].push_back(y);
        T[y].push_back(x);
    }

    for(int i=1;i<=N;i++)
        if(!visited[i])
            DFS1(i);

    memset(visited,false,sizeof visited);
    while(!Stack.empty())
    {
        if(!visited[Stack.top()])
            nSol++, DFS2(Stack.top());
        Stack.pop();
    }

    fout<<nSol<<"\n";
    for(int i=1;i<=nSol;i++)
    {
        for(auto x : sol[i])
            fout<<x<<" ";
        fout<<"\n";
    }
    return 0;
}