#include<cstdio>
#include<vector>
#define MAX_N 100000
using namespace std;

vector<int>g[MAX_N+1], gt[MAX_N+1], scc[MAX_N+1];
int f[MAX_N+1], n, m, numSCC, k;
bool used[MAX_N+1];

void readGraph() {
    int i, x, y;
    FILE* fin = fopen("ctc.in","r");
    fscanf(fin,"%d%d",&n,&m);
    for(i = 0; i < m; i++) {
        fscanf(fin,"%d%d",&x,&y);
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    fclose(fin);
}

void DFS(int node) {
    used[node] = true;
    for(auto i : g[node])
        if(!used[i])
            DFS(i);
    f[k++] = node;
}

void DFS_master() {
    for(int i = 1; i <= n; i++)
        if(!used[i])
            DFS(i);
}

void DFSreverseGraph(int node) {
    used[node] = true;
    scc[numSCC].push_back(node);
    for(auto i : gt[node])
        if(!used[i])
            DFSreverseGraph(i);
}

void Kosaraju() {
    int i;
    for(i = 1; i <= n; i++)
        used[i] = false;
    for(i = n-1; i >= 0; i--) {
        if(!used[f[i]]) {
            DFSreverseGraph(f[i]);
            numSCC++;
        }
    }
}

void printSCC() {
    FILE* fout = fopen("ctc.out","w");
    fprintf(fout,"%d\n",numSCC);
    for(int i = 0; i < numSCC; i++) {
        for(int j = 0; j < scc[i].size(); j++)
            fprintf(fout,"%d ",scc[i][j]);
        fprintf(fout,"\n");
    }
    fclose(fout);
}

int main() {
    readGraph();
    DFS_master();
    Kosaraju();
    printSCC();
    return 0;
}