#include <bits/stdc++.h>
#define pb push_back

using namespace std;

const int MAXN = 100010;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, m, nr, k, ord[MAXN], ll[MAXN];
bool inSt[MAXN];
vector<int> edges[MAXN], comp[MAXN];
stack<int> st;

void read() {
    fin >> n >> m;
    for (int i = 0; i < m; ++i) {
        int x, y;
        fin >> x >> y;
        edges[x].pb(y);
    }
}

void dfs(int node) {
    st.push(node);
    inSt[node] = 1;
    ll[node] = ord[node] = ++k;
    for (vector<int>::iterator it = edges[node].begin(); it != edges[node].end(); ++it)
        if (!ord[*it]) {
            dfs(*it);
            ll[node] = min(ll[node], ll[*it]);
        }
        else if (inSt[*it])
            ll[node] = min(ll[node], ord[*it]);
    if (ll[node] == ord[node]) {
        while (!st.empty()) {
            int top = st.top();
            st.pop();
            inSt[top] = 0;
            comp[nr].pb(top);
            if (top == node)
                break;
        }
        ++nr;
    }
}

void testPrint() {
    for (int i = 0; i < n; ++i)
        cout << ord[i + 1] << ' ' << ll[i + 1] << '\n';
}

void print() {
    fout << nr << '\n';
    for (int i = 0; i < nr; ++i) {
        for (vector<int>::iterator it = comp[i].begin(); it != comp[i].end(); ++it)
            fout << *it << ' ';
        fout << '\n';
    }

}

int main() {
    read();
    for (int i = 1; i <= n; ++i)
        if (!ord[i])
            dfs(i);
    print();
    testPrint();
    return 0;
}