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

const int NMAX = 100010;

int N, M, A, B, TopSort[NMAX];
vector<int> G[NMAX], GT[NMAX], CrtCTC;
bool Used[NMAX];
vector<vector<int> > Ans;

void DFP(int Node)
{
    Used[Node] = 1;

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

void DFM(int Node)
{
    Used[Node] = 0;
    CrtCTC.push_back(Node);

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

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", &A, &B);
        G[A].push_back(B);
        GT[B].push_back(A);
    }

    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]);
            Ans.push_back(CrtCTC);
        }

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