#include<stdio.h>
#include<vector>
#include<algorithm>
#define MAXN 100001

using namespace std;

int n,m,i,nrc,N,j;
int coada[MAXN],v1[MAXN],v2[MAXN];
vector <int> a[MAXN],at[MAXN],ctc[MAXN];

void dfs(int nod)
{
    int i;
    v1[nod]=1;
    for(i=0;i<a[nod].size();i++)
    if(!v1[a[nod][i]])
        dfs(a[nod][i]);
    coada[++N]=nod;
}

void dfst(int nod)
{
    int i;
    v2[nod]=1;
    ctc[nrc].push_back(nod);
    for(i=0;i<at[nod].size();i++)
    if(!v2[at[nod][i]])
        dfst(at[nod][i]);
}


int main(void)
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&n,&m);
    int x,y;
    for(i=1;i<=m;i++)
    {
        scanf("%d%d",&x,&y);
        a[x].push_back(y);
        at[y].push_back(x);
    }
    for(i=1;i<=n;i++)
    if(!v1[i])
        dfs(i);
    for(i=N;i>=1;i--)
    if(!v2[coada[i]])
    {
        nrc++;
        dfst(coada[i]);
    }
    printf("%d\n",nrc);
    for(i=1;i<=nrc;i++)
    {
        for(j=0;j<ctc[i].size();j++)
            printf("%d ",ctc[i][j]);
        printf("\n");
    }
    return 0;
}