#include<stdio.h>
#include<vector>
using namespace std;
#define nmax  100005
int n, m, i, a, b, tp, comp;
int viz[nmax], v[nmax];
vector <int> ma[nmax], mat[nmax], vcomp[nmax];
vector <int> ::iterator it;

void citire()
{
    scanf("%ld %ld",&n,&m);
    for (i=1;i<=m;i++)
    {
        scanf("%ld %ld",&a,&b);
        ma[a].push_back(b); mat[b].push_back(a);
    }
}

void dfs1(int x)
{
    vector <int> ::iterator it;
    viz[x]=1;
    for (it=ma[x].begin();it!=ma[x].end();it++)
        if (!viz[*it])
            dfs1(*it);
    v[++tp]=x;
}

void dfs2(int x)
{
    vector <int> ::iterator it;
    viz[x]=2;
    vcomp[comp].push_back(x);
    for (it=mat[x].begin();it!=mat[x].end();it++)
        if (viz[*it]<2)
            dfs2(*it);
}

void afisare()
{
    printf("%ld\n",comp);
    for (i=1;i<=comp;i++)
    {
        for (it=vcomp[i].begin();it!=vcomp[i].end();it++)
            printf("%ld ",*it);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    for (i=1;i<=n;i++)
        if (!viz[i])
            dfs1(i);
    for (i=n;i>=1;i--)
        if (viz[v[i]]<2)
        {
            comp++;
            dfs2(v[i]);
        }
    afisare();
    return 0;
}