#include <stdio.h>
#include <vector>

using namespace std;

vector<int> v, g[100001], _g[100001], sol[100001];
bool viz[100001]={0}, _viz[100001]={0};
int n, nr, nrc;

void dfs(int nod)
{
    viz[nod]=true;
    v.push_back(nod);
    for(int i=0; i<g[nod].size(); i++)
        if(!viz[g[nod][i]])
            dfs(g[nod][i]);
}

void dfs2(int nod)
{
    _viz[nod]=true;
    sol[nrc].push_back(nod);
    int l=_g[nod].size();
    for(int i=0; i<l; i++)
        if(viz[_g[nod][i]] && !_viz[_g[nod][i]])
            dfs2(_g[nod][i]);
}
char buff[200000];int pos=0;
FILE*f=freopen("ctc.in","r",stdin);
FILE*gg=freopen("ctc.out","w",stdout);
inline void read(int &nr){
    while(buff[pos] < '0' || buff[pos] > '9')if(++pos == 200000) fread(buff, 1, 200000, stdin), pos = 0;
    nr = 0;
    while('0' <= buff[pos] && buff[pos] <= '9') {nr = nr * 10 + buff[pos] - '0';if(++pos == 200000) fread(buff, 1, 200000, stdin), pos = 0;}
}
int main()
{
    int m, a, b, lg, i, j;
    fread(buff, 1, 200000, stdin);
    read(n);read(m);
    for(i=1; i<=m; i++)
    {
        read(a);read(b);
        g[a].push_back(b);
        _g[b].push_back(a);
    }
    for(i=1; i<=n; i++)
        if(!viz[i])
        {
            dfs(i);
            lg=v.size();
            for(j=0; j<lg; j++)
            {
                if(!_viz[v[j]])
                {
                    nrc++;
                    dfs2(v[j]);
                }
            }
        }
    printf("%d\n", nrc);
    for(i=1; i<=nrc; i++)
    {
        lg=sol[i].size();
        for(j=0; j<lg; j++)
            printf("%d ", sol[i][j]);
        printf("\n");
    }
}