#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");
int n, m, cnt;
vector<int> v[100005];
vector<int> inv[100005];
int viz[100005];
vector<int> ord;
vector<int> ans[100005];

void dfs1(int node)
{
    viz[node] = 1;

    for(auto it: v[node])
    {
        if(viz[it] == 0)
        {
            dfs1(it);
        }
    }

    ord.push_back(node);
}

void dfs2(int node)
{
    viz[node] = 1;
    ans[cnt].push_back(node);

    for(auto it: inv[node])
    {
        if(viz[it] == 0)
        {
            dfs2(it);
        }
    }
}

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

    int x, y;
    for(int i = 1; i<=m; i++)
    {
        in>>x>>y;

        v[x].push_back(y);
        inv[y].push_back(x);
    }

    for(int i = 1; i<=n; i++)
    {
        if(viz[i] == 0)
        {
            dfs1(i);
        }
    }

    reverse(ord.begin(), ord.end());

    for(int i = 1; i<=n; i++)
    {
        viz[i] = 0;
    }

    for(auto it: ord)
    {
        if(viz[it] == 0)
        {
            cnt++;
            dfs2(it);
        }
    }

    out<<cnt<<'\n';
    for(int i = 1; i<=cnt; i++)
    {
        for(auto it: ans[i])
        {
            out<<it<<" ";
        }
        out<<'\n';
    }

    return 0;
}