#include <stdio.h>
#include <vector>
#include <stack>
using namespace std;
FILE *fin = fopen("ctc.in", "r");
FILE *fout = fopen("ctc.out", "w");
vector <int> muchied[100001];
vector <int> muchiei[100001];
vector<int> componenta[100001];
stack <int> stiva;
char mark[100001];
char introdus[100001];
void dfs (int nod)
{
    mark[nod]=1;
    for(auto node : muchied[nod])
    {
        if(mark[node] == 0)
        {
            dfs(node);
        }
    }
    stiva.push(nod);
}
void ctc(int x, int y)
{
    if(introdus[x]==0)
    {
        introdus[x]=1;
        componenta[y].push_back(x);
        for(auto node : muchiei[x])
        {
            ctc(node,y);
        }
    }
}
int main()
{
    int n,m;
    fscanf(fin, "%d%d", &n, &m);
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fscanf(fin, "%d%d", &x, &y);
        muchied[x].push_back(y);
        muchiei[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
    {
        if(mark[i]==0) dfs(i);
    }
    while(!stiva.empty())
    {
        int nod = stiva.top();
        stiva.pop();
        ctc(nod,nod);
    }
    int nrcomp = 0;
    for(int i=1;i<=n;i++)
    {
        if(!componenta[i].empty())
        {
            nrcomp ++;
        }
    }
    fprintf(fout, "%d\n", nrcomp);
    for(int i=1;i<=n;i++)
    {
        if(!componenta[i].empty())
        {
            for(auto node : componenta[i]) fprintf(fout, "%d ", node);
            fprintf(fout, "\n");
        }
    }
    return 0;
}