#include <cstdio>
#include <vector>

using namespace std;
int n,m,i,j,t,x,y,k,componente,d[100005],st[100005],nrparcurs[100005];
bool instiva[100005];

vector <int> v[100005],sol[100005];

void dfs(int nod)
{
    int i;
    t++;
    nrparcurs[nod]=d[nod]=t;
    st[++k]=nod;
    instiva[nod]=1;
    for (i=0; i<v[nod].size(); i++)
        if (d[v[nod][i]]==0)
    {
        dfs(v[nod][i]);
        d[nod]=min(d[nod],d[v[nod][i]]);
    }
        else if (instiva[v[nod][i]]==1)
            d[nod]=min(d[nod],nrparcurs[v[nod][i]]);
    if (d[nod]==nrparcurs[nod])
    {
        componente++;
        int vf;
        do
        {
            vf=st[k];
            k--;
            instiva[vf]=0;
            sol[componente].push_back(vf);
        } while (vf!=nod);
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&n,&m);
    for (i=1; i<=m; i++)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
    }
    for (i=1; i<=n; i++)
        if (d[i]==0) dfs(i);
    printf("%d\n",componente);
    for (i=1; i<=componente; i++)
    {
        for (j=0; j<sol[i].size(); j++)
            printf("%d ",sol[i][j]);
        printf("\n");
    }
    return 0;
}