#include <bits/stdc++.h>
using namespace std;
vector <int> graf1[100005];
vector <int> graf2[100005];
vector <int> sortop;
vector <int> comp[100005];
bool viz1[100005];
bool viz2[100005];
int comp_curenta;
int n,m;
ifstream in("ctc.in");
ofstream out("ctc.out");

void dfs1(int s)
{
    viz1[s]=1;
    for(auto el:graf1[s])
    {
        if(viz1[el]==0)
        {
            dfs1(el);
        }
    }
    sortop.push_back(s);
}

void dfs2(int s)
{
    viz2[s] = 1;
    comp[comp_curenta].push_back(s);
    for(auto el:graf2[s])
    {
        if(viz2[el]==0)
        {
            dfs2(el);
        }
    }
}

int main()
{
   in>>n>>m;
    int x,y;
    for(int i=0;i<m;i++)
    {
        in>>x>>y;
        graf1[x].push_back(y);
        graf2[y].push_back(x);
    }

    for(int i=1; i<=n; i++)
    {
        if(viz1[i]==0)
        {
            dfs1(i);
        }
    }
    reverse(sortop.begin(),sortop.end());
    for(int i:sortop)
    {
        if(viz2[i]==0)
        {
            dfs2(i);
            comp_curenta++;
        }
    }
    out<<comp_curenta<<'\n';
    for(int i=0; i<comp_curenta; i++)
    {
        for(int j = 0; j < comp[i].size(); j++)
        {
            out<<comp[i][j]<<" ";

        }
        out<<'\n';
    }
    return 0;
}