#include <cstdio>
#include <vector>
#define NMAX 100000
using namespace std;

int n,m,i,nr=0;
vector <int> v,sol[NMAX+5],G[NMAX+5],GT[NMAX+5];
bool ok[NMAX+5];

void dfs(int node)
{
    int s,i,x;

    ok[node]=1;
    s=G[node].size();

    for(i=0;i<s;++i)
    {
        x=G[node][i];
        if(!ok[x])
            dfs(x);
    }

    v.push_back(node);
}

void dfst(int node)
{
    int s,i,x;

    ok[node]=0;
    s=GT[node].size();
    sol[nr].push_back(node);

    for(i=0;i<s;++i)
    {
        x=GT[node][i];
        if(ok[x])
            dfst(x);
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);

    scanf("%d%d",&n,&m);

    for(i=1;i<=m;++i)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        G[a].push_back(b);
        GT[b].push_back(a);
    }

    for(i=1;i<=n;++i)
        if(!ok[i])
          dfs(i);

    while(!v.empty())
    {
        i=v.back();
        v.pop_back();
        if(ok[i])
        {
            ++nr;
            dfst(i);
        }
    }

    printf("%d\n",nr);
    for(i=1;i<=nr;++i)
    {
        int j,s=sol[i].size();
        for(j=0;j<s;++j)
            printf("%d ",sol[i][j]);
        printf("\n");
    }

    return 0;
}