#include <stack>
#include <vector>
#include <cstdio>
#include <bitset>
#include <algorithm>
#define nmax 100005
using namespace std;
vector<int> gr[nmax],tr[nmax];
vector<int> ctc[nmax];
bitset<nmax> b;
stack<int> s;
int n,m,a;

void dfsgraph(int node)
{
    int i;
    b[node]=1;
    for(i=0;i<gr[node].size();i++)
        if(!b[gr[node][i]])
            dfsgraph(gr[node][i]);
    s.push(node);
}

void dfstrans(int node)
{
    int i;
    b[node]=1;
    ctc[a].push_back(node);
    for(i=0;i<tr[node].size();i++)
        if(!b[tr[node][i]])
            dfstrans(tr[node][i]);
}

int main()
{
    int i,x,y,j;
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d %d",&n,&m);
    for(i=1;i<=m;i++)
    {
        scanf("%d %d",&x,&y);
        gr[x].push_back(y);
        tr[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(!b[i])
            dfsgraph(i);
    b.reset();
    while(!s.empty())
    {
        x=s.top();
        s.pop();
        if(b[x]==0)
        {
            a++;
            dfstrans(x);
        }
    }
    printf("%d\n",a);
    for(i=1;i<=a;i++)
    {
        sort(ctc[i].begin(),ctc[i].end());
        for(j=0;j<ctc[i].size();j++)
            printf("%d ",ctc[i][j]);
        printf("\n");
    }
    return 0;
}