#include<stdio.h>
#include<string.h>
#include<vector>
#include<stack>
using namespace std;

const int NMAX = 1e5;

vector <int> graph[NMAX + 5], trans[NMAX + 5], comp[NMAX + 5];
stack <int> st;

int vis[NMAX + 5];
int n, ncomp; 

void plus (int node) {
    vis[node] = 1;
    for(vector <int>::iterator it = graph[node].begin(); it != graph[node].end(); ++ it)
        if(!vis[*it])
            plus(*it);
    st.push(node);
}

void minus (int node) {
    vis[node] = ncomp;
    comp[ncomp].push_back(node);

    for(vector <int>::iterator it = trans[node].begin(); it != trans[node].end(); ++ it)
        if(!vis[*it])
            minus(*it);
}

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

    scanf("%d%d", &n, &m);
    for(i = 1; i <= m; ++ i) {
        scanf("%d%d", &x, &y);

        graph[x].push_back(y);
        trans[y].push_back(x);
    }

    for(i = 1; i <= n; ++ i)
        if(!vis[i])
            plus(i);
 
    memset(vis, 0, sizeof(vis));
    ncomp = 0;
    while(!st.empty()) {
        if(vis[st.top()]) {
            st.pop();
            continue;
        }

        ++ ncomp;
        minus(st.top());
        st.pop();
    }

    printf("%d\n", ncomp);
    for(i = 1; i <= ncomp; ++ i, printf("\n"))
        for(vector <int>::iterator it = comp[i].begin(); it != comp[i].end(); ++ it)
            printf("%d ", *it);
    return 0;
}