#include <cstdio>
#include <cstring>
#include <vector>
#define nmax 100005
using namespace std;

vector <int> g[nmax],gt[nmax],ctc[nmax];
bool used[nmax];
int st[nmax],sol=0;

inline void dfs(int nod)
{
    used[nod]=true;
    for (int i=0;i<g[nod].size();i++)
        if (!used[ g[nod][i] ]) dfs(g[nod][i]);
    st[++st[0]]=nod;
}

inline void dfst(int nod)
{
    used[nod]=true;
    for (int i=0;i<gt[nod].size();i++)
        if (!used[ gt[nod][i] ]) dfst(gt[nod][i]);
    ctc[sol].push_back(nod);
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    int n,m,i,x,y;
    scanf("%d %d",&n,&m);
    for (i=1;i<=m;i++)
    {
        scanf("%d %d",&x,&y);
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    memset(used,false,sizeof(used));
    memset(st,0,sizeof(st));
    for (i=1;i<=m;i++)
        if (!used[i]) dfs(i);
    memset(used,false,sizeof(used));
    for (i=n;i>0;i--)
        if (!used[st[i]])
        {
            sol++;
            dfst(st[i]);
        }
    printf("%d\n",sol);
    for (i=1;i<=sol;i++)
    {
        for (int j=0;j<ctc[i].size();j++)
            printf("%d ",ctc[i][j]);
        printf("\n");
    }
    return 0;
}