#include <cstdio>
#include <vector>
#include <cstring>

#define N_MAX 100000

using namespace std;

int n, ctc;
vector<int> G[N_MAX];
vector<int> GT[N_MAX];

vector<int> S1;
vector<int> COMP[N_MAX];

bool viz[N_MAX];

void read() {
    freopen("ctc.in", "r", stdin);
    int m;
    scanf("%d %d", &n, &m);
    for(int i = 0; i < m; i++) {
        int a, b;
        scanf("%d %d", &a, &b);
        a--; b--;
        G[a].push_back(b);
        GT[b].push_back(a);
    }
    fclose(stdin);
}

void top_sort(int x) {
    viz[x] = true;
    for(vector<int>::iterator it = GT[x].begin(); it != GT[x].end(); it++) {
        if(!viz[*it]) top_sort(*it);
    }
    S1.push_back(x);
}

void dfs(int x) {
    viz[x] = true;
    for(vector<int>::iterator it = G[x].begin(); it != G[x].end(); it++) {
        if(!viz[*it]) dfs(*it);
    }
    COMP[ctc].push_back(x);
}

int main() {
    read();
    for(int i = 0; i < n; i++) {
        if(!viz[i]) top_sort(i);
    }
    memset(viz, false, sizeof(viz));
    while(!S1.empty()) {
        if(!viz[S1.back()]) {
            dfs(S1.back());
            ctc++;
        }
        S1.pop_back();
    }

    freopen("ctc.out", "w", stdout);
    printf("%d\n", ctc);
    for(int i = 0; i < ctc; i++) {
        while(!COMP[i].empty()) {
            printf("%d ", COMP[i].back() + 1);
            COMP[i].pop_back();
        }
        printf("\n");
    }
    fclose(stdout);
    return 0;
}