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

#define Nmax 100010
#define pb push_back
#define forit(it, v) for(typeof((v).begin()) it = (v).begin(); it != (v).end(); ++ it)

int N, M, X, Y, TopSort[Nmax], SCC[Nmax], CrtSCC;
vector<int> G[Nmax], GT[Nmax];
vector<vector<int> > Comp;
bool Used[Nmax];

void DFS_First(int Node)
{
    Used[Node] = 1;
    forit(it, G[Node])
        if(!Used[*it])
            DFS_First(*it);
    TopSort[++TopSort[0]] = Node;
}

void DFS_Second(int Node)
{
    Used[Node] = 0;
    forit(it, GT[Node])
        if(Used[*it])
            DFS_Second(*it);
    SCC[Node] = SCC[0];
}

void Kosaraju()
{
    for(int i = 1; i <= N; ++ i)
        if(!Used[i])
            DFS_First(i);
    reverse(TopSort + 1, TopSort + TopSort[0] + 1);
    for(int i = 1; i <= N; ++ i)
        if(Used[TopSort[i]])
        {
            SCC[0] ++;
            DFS_Second(TopSort[i]);
        }
    Comp = vector<vector<int> > (SCC[0], vector<int>());
    for(int i = 1; i <= N; ++ i) Comp[SCC[i] - 1].pb(i);
    printf("%i\n", SCC[0]);
    for(int i = 0; i < SCC[0]; ++ i)
    {
        for(int j = 0; j < Comp[i].size(); ++ j)
            printf("%i ", Comp[i][j]);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    int i;
    scanf("%i %i", &N, &M);
    for(i = 1; i <= M; ++ i)
    {
        scanf("%i %i", &X, &Y);
        G[X].pb(Y);
        GT[Y].pb(X);
    }
    Kosaraju();
    return 0;
}