#include <bits/stdc++.h>

using namespace std;
const int MAX = 2e5 +10;
vector<int>g[MAX],gt[MAX];
stack<int>s;
vector<vector<int>>ans;
vector<bool>used;
int n,m;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
void dfs1(int node)
{
    if(used[node])
        return;
    used[node] = 1;
    for(auto x : g[node])
        dfs1(x);
    s.push(node);
}
void dfs2(int node,vector<int>&r)
{
    if(used[node])
        return;
    used[node]=1;r.push_back(node);
    for(auto x:gt[node])
        dfs2(x,r);
}
int32_t main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin>>x>>y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    used.assign(n+1, false);
    for(int i=1;i<=n;i++)
        if(!used[i])
            dfs1(i);
    used.assign(n+1,false);
    for(;!s.empty();s.pop())
    {
        if(!used[s.top()])
        {
            vector<int>r;
            dfs2(s.top(),r);
            ans.push_back(r);
        }
    }
    fout<<ans.size()<<'\n';
    for(int i=0;i<ans.size();i++,fout<<'\n')
        for(auto x:ans[i])
            fout<<x<<' ';
}