#include <bits/stdc++.h>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

int n,m,k,x,y,viz[100200];
vector <int> edges[100200],tedges[100200];
stack <int> st;
vector <int> w[100200];

void dfs(int x)
{
    viz[x]=1;
    for(auto y:edges[x])
        if(viz[y]==0)
            dfs(y);
    st.push(x);
}

void dfs2(int x)
{
    viz[x]=k;
    w[k].push_back(x);
    for(auto y:tedges[x])
        if(viz[y]==0)
            dfs2(y);
}

int32_t main()
{
    f>>n>>m;
    for(int i=1; i<=m; i++)
        f>>x>>y, edges[x].push_back(y), tedges[y].push_back(x);
    for(int i=1; i<=n; i++)
        if(viz[i]==0)
            dfs(i);
    memset(viz,0,sizeof(viz));
    while(!st.empty())
    {
        int x=st.top();
        if(viz[x]==0)
            k++, dfs2(x);
        st.pop();
    }
    g<<k<<'\n';
    for(int i=1; i<=k; i++, g<<'\n')
        for(auto it:w[i])
            g<<it<<' ';
    return 0;
}