#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int long long
#define double long double
#define endl '\n'
#define sz size
#define pb push_back
#define fs first
#define sc second
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
int const INF = LONG_LONG_MAX;

int n, m, ans=0;
vector<bool> mark;
vector<int> ord, vec[100005], adj[100005], rev_adj[100005];

void dfs1(int v)
{
    mark[v]=1;
    for(int x:adj[v])
    {
        if(!mark[x]) dfs1(x);
    }
    ord.pb(v);
}

void dfs2(int v)
{
    mark[v]=1;
    vec[ans].pb(v);
    for(int x:rev_adj[v])
    {
        if(!mark[x]) dfs2(x);
    }
}

void solve()
{
    cin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int a, b;
        cin>>a>>b;
        adj[a].pb(b);
        rev_adj[b].pb(a);
    }

    mark.assign(n+5, 0);
    for(int i=1;i<=n;i++)
    {
        if(!mark[i]) dfs1(i);
    }
    reverse(all(ord));
    mark.assign(n+5, 0);
    for(int x:ord)
    {
        if(!mark[x]){ans++;dfs2(x);}
    }
    cout<<ans<<endl;
    for(int i=1;i<=ans;i++)
    {
        for(int x:vec[i])
        {
            cout<<x<<' ';
        }
        cout<<endl;
    }
}

int32_t main()
{
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    int tc=1;
    //cin>>tc;
    while(tc--)
    {
        solve();
    }
    return 0;
}