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

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

void readGraph() {
    int x, y;
    FILE* fin = fopen("ctc.in","r");
    fscanf(fin,"%d%d",&n,&m);
    for(int 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 x) {
    used[x] = true;
    for(auto i : g[x])
        if(!used[i])
            DFS(i);
    st[head++] = x;
}

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

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

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

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

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