#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

vector<int> G[2][100001];
bool viz[2][100001];
vector<int> ord;
vector<int> comp[100001];

void dfs(int root) {
    viz[0][root] = true;
    for(auto it: G[0][root])
        if(!viz[0][it])
            dfs(it);
    ord.push_back(root);
}

void dfs_rev(int root, int c) {
    viz[1][root] = true;
    comp[c].push_back(root);
    for (auto it: G[1][root])
        if(!viz[1][it])
            dfs_rev(it, c);
}

int main() {
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);

    int N, M;
    scanf("%d %d", &N, &M);
    while(M --) {
        int a, b;
        scanf("%d %d", &a, &b);
        G[0][a].push_back(b);
        G[1][b].push_back(a);
    }

    for(int i = 1; i <= N; i ++)
        if(!viz[0][i]) 
            dfs(i);

    int C = 0;
    reverse(ord.begin(), ord.end());
    for(auto it: ord)
        if(!viz[1][it])
            dfs_rev(it, C++);

    printf("%d\n", C);
    for (int cmp = 0; cmp < C; cmp ++) {
        for(auto it: comp[cmp])
            printf("%d ", it);
        printf("\n");
    }
    return 0;
}