#include <cstdio>
#include <cstring>
#include <vector>
#include <deque>
using namespace std;
#define Max 100000
vector<int>g[Max],t[Max];
deque<deque<int> >d;
deque<int>s;

int n;
bool was[Max],st[Max],dr[Max];

void dfs_st(int x)
{
    int y;
    st[x]=1;
    for(int i=0;i<g[x].size();i++)
    {
        y=g[x][i];
        if(!st[y])dfs_st(y);
    }
}

void dfs_dr(int x)
{
    int y;
    dr[x]=1;
    for(int i=0;i<t[x].size();i++)
    {
        y=t[x][i];
        if(!dr[y])dfs_dr(y);
    }
}

void ctc()
{
    for(int i=1;i<=n;i++)
    if(!was[i])
    {
        memset(st,0,sizeof(st));
        memset(dr,0,sizeof(dr));
        dfs_st(i);
        dfs_dr(i);
        s.clear();
        for(int j=1;j<=n;j++)
        if(st[j] && dr[j])
        {
            was[j]=1;
            s.push_back(j);
        }
        if(s.size()>0)d.push_back(s);
    }
    printf("%d\n",d.size());
    while(d.size()>0)
    {
        s=d.front();
        d.pop_front();
        while(s.size()>0)
        {
            printf("%d ",s.front());
            s.pop_front();
        }
        printf("\n");
    }
}

int main()
{
    int m,x,y;
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d %d",&n,&m);
        while(m--)
        {
            scanf("%d %d",&x,&y);
            g[x].push_back(y);
            t[y].push_back(x);
        }
        ctc();
    return 0;
}