#include <cstdio>
#include <vector>
#include <stack>
#include <cstring>
#define NMAX 100010

using namespace std;

vector<int> G[NMAX],iG[NMAX];
vector< vector<int> > C;
stack<int> st;
int n,m,sol,viz[NMAX];

void DFS(int nod)
{
    viz[nod]=1;
    for(int i=0;i<G[nod].size();i++)
        if(!viz[G[nod][i]]) DFS(G[nod][i]);

    st.push(nod);
}
void iDFS(int nod)
{
    viz[nod]=1;
    C[sol].push_back(nod);
    for(int i=0;i<iG[nod].size();i++)
        if(!viz[iG[nod][i]]) iDFS(iG[nod][i]);
}

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

    scanf("%d%d",&n,&m);
    for(i=0;i<m;i++)
    {
        scanf("%d%d",&a,&b);
        G[a].push_back(b);
        iG[b].push_back(a);
    }

    for(i=1;i<=n;i++)
        if(!viz[i]) DFS(i);

    memset(viz,0,sizeof(viz));
    for(;!st.empty();st.pop())
        if(!viz[st.top()])
        {
            C.push_back(vector<int>());
            iDFS(st.top()),sol++;
        }

    printf("%d\n",sol);
    for(i=0;i<sol;i++,printf("\n"))
        for(a=0;a<C[i].size();a++)
            printf("%d ",C[i][a]);
}