#include <bits/stdc++.h>

#if 1
#define pv(x) cout<<#x<<" = "<<x<<"; ";cout.flush()
#define pn cout<<endl
#else
#define pv(x)
#define pn
#endif

using namespace std;
ifstream in("ctc.in");
ofstream out("ctc.out");

using ll = long long;
using ull = unsigned long long;
using uint = unsigned int;
#define pb push_back
#define mp make_pair
const int NMax = 1e5 + 5;
const int inf = 1e9 + 5;
using zint = int;

int N,M,nrComp;
bool inStack[NMax],inComp[NMax];
vector<int> v[NMax],rev[NMax],comp[NMax];
stack<int> st;

void buildStack(int);
void getComp(int);

int main() {
    in>>N>>M;
    for (int i = 1;i <= M;++i) {
        int x,y;
        in>>x>>y;

        v[x].pb(y);
        rev[y].pb(x);
    }

    for (int i = 1;i <= N;++i) {
        if (inStack[i]) {
            continue;
        }

        buildStack(i);
    }

    while (st.size()) {
        int node = st.top();
        st.pop();

        if (inComp[node]) {
            continue;
        }

        ++nrComp;
        getComp(node);
    }

    out<<nrComp<<'\n';
    for (int i = 1;i <= nrComp;++i) {
        for (int node : comp[i]) {
            out<<node<<' ';
        }
        out<<'\n';
    }

    in.close();out.close();
    return 0;
}

void buildStack(int node) {
    inStack[node] = true;

    for (int nxt : v[node]) {
        if (inStack[nxt]) {
            continue;
        }

        buildStack(nxt);
    }

    st.push(node);
}

void getComp(int node) {
    inComp[node] = true;
    comp[nrComp].pb(node);

    for (int nxt : rev[node]) {
        if (inComp[nxt]) {
            continue;
        }

        getComp(nxt);
    }
}