#include <cstdio>
#include <bitset>
#include <vector>
#define NMAX 100001
#define INF (1 << 30) 
using namespace std;
bitset<NMAX> onStack;
vector<int> children[NMAX];
vector<vector<int> > solution;
vector<int> st;
int n, m, count, index[NMAX], minim[NMAX];
void readInput() {
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    int a, b;
    scanf("%d %d", &n, &m);
    for (int i = 0; i < m; i++) {
        scanf("%d %d", &a, &b);
        children[a].push_back(b);
    }
    for (int i = 1; i <= n; i++) {
        index[i] = INF;
    }
}
void push(int idx) {
    onStack[idx] = 1;
    index[idx] = minim[idx] = ++count;
    st.push_back(idx);
}
void pop(int idx) {
    if (minim[idx] == index[idx]) {
        int top;
        solution.push_back(vector<int>());
        do {
            top = st.back();
            onStack[top] = 0;
            st.pop_back();
            solution.back().push_back(top);
        } while (top != idx);
    }
}
void visit(int idx) {
    push(idx);
    for (size_t i = 0; i < children[idx].size(); i++) {
        int child = children[idx][i];
        if (index[child] == INF) {
            visit(child);
            minim[idx] = min(minim[idx], minim[child]);
        } else if (onStack[child]) {
            minim[idx] = min(minim[idx], index[child]);
        }
    }
    pop(idx);
}
int main() {
    readInput();
    for (int i = 1; i <= n; i++) {
        if (index[i] == INF) {
            visit(i);
        }
    }
    printf("%u\n", solution.size());
    for (size_t i = 0; i < solution.size(); i++) {
        for (size_t j = 0; j < solution[i].size(); j++) {
            printf("%d ", solution[i][j]);
        }
        printf("\n");
    }
    return 0;
}