#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 st[MAX_N + 1], n, m, numScc, vf;
bool used[MAX_N + 1];

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 node) {
    vector<int>::iterator it;
    used[node] = true;
    for(it = G[node].begin(); it != G[node].end(); it++) {
        if(!used[*it])
            DFS(*it);
    }
    st[vf++] = node;
}

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

void DFS_reverseGraph(int node) {
    vector<int>::iterator it;
    used[node] = true;
    scc[numScc].push_back(node);
    for(it = Gt[node].begin(); it != Gt[node].end(); it++) {
        if(!used[*it])
            DFS_reverseGraph(*it);
    }
}

void Kosaraju() {
    DFS_master();
    for(int i = 1; i <= n; i++)
        used[i] = false;
    for(int i = vf - 1; i >= 0; i--) {
        if(!used[st[i]]) {
            DFS_reverseGraph(st[i]);
            numScc++;
        }
    }
}

void printSCC() {
    FILE *fout = fopen("ctc.out","w");
    fprintf(fout,"%d\n",numScc);
    for(int i = 0; i < numScc; i++) {
        for(vector<int>::iterator it = scc[i].begin(); it != scc[i].end(); it++)
            fprintf(fout,"%d ",*it);
        fprintf(fout,"\n");
    }
    fclose(fout);
}

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