#include <cstdio>
#include <cstdlib>
#include <vector>
#include <algorithm>
using namespace std;

const int NMAX = 100010;

int N, M, X, Y, TopSort[NMAX];
bool Used[NMAX];
vector<int> G[NMAX], GT[NMAX], CrtCTC;
vector<vector<int> > CTC;

void DFP(int Node)
{
    Used[Node] = 1;
    for(int i = 0; i < G[Node].size(); ++ i)
        if(!Used[ G[Node][i] ])
            DFP(G[Node][i]);
    TopSort[++ TopSort[0]] = Node;
}

void DFM(int Node)
{
    Used[Node] = 0;
    CrtCTC.push_back(Node);
    for(int i = 0; i < GT[Node].size(); ++ i)
        if(Used[ GT[Node][i] ])
            DFM(GT[Node][i]);
}

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

    scanf("%i %i", &N, &M);
    for(int i = 1; i <= M; ++ i)
    {
        scanf("%i %i", &X, &Y);
        G[X].push_back(Y);
        GT[Y].push_back(X);
    }

    for(int i = 1; i <= N; ++ i)
        if(!Used[i])
            DFP(i);

    for(int i = TopSort[0]; i; -- i)
        if(Used[TopSort[i]])
        {
            CrtCTC.clear();
            DFM(TopSort[i]);
            CTC.push_back(CrtCTC);
        }

    printf("%i\n", CTC.size());
    for(int i = 0; i < CTC.size(); ++ i)
    {
        for(int j = 0; j < CTC[i].size(); ++ j)
            printf("%i ", CTC[i][j]);
        printf("\n");
    }
}