#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
constexpr int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

struct StronglyConnectedComponents {
  std::vector<int> id;
  std::vector<std::vector<int>> vertices, comp;

  StronglyConnectedComponents(const std::vector<std::vector<int>> &graph, bool heavy = false) : graph(graph), heavy(heavy) {
    n = graph.size();
    rev_graph.resize(n);
    for (int i = 0; i < n; ++i) for (int e : graph[i]) rev_graph[e].emplace_back(i);
    used.assign(n, false);
    id.assign(n, -1);
    for (int i = 0; i < n; ++i) {
      if (!used[i]) dfs(i);
    }
    int now = 0;
    for (int i = n - 1; i >= 0; --i) {
      if (id[order[i]] == -1) {
        if (heavy) vertices.emplace_back();
        rev_dfs(order[i], now++);
      }
    }
    comp.resize(now);
    for (int i = 0; i < n; ++i) for (int e : graph[i]) {
      if (id[i] != id[e]) comp[id[i]].emplace_back(id[e]);
    }
    // if (heavy) {
    //   for (int i = 0; i < now; ++i) std::sort(vertices[i].begin(), vertices[i].end());
    // }
  }

private:
  bool heavy;
  int n;
  std::vector<std::vector<int>> graph, rev_graph;
  std::vector<bool> used;
  std::vector<int> order;

  void dfs(int ver) {
    used[ver] = true;
    for (int e : graph[ver]) {
      if (!used[e]) dfs(e);
    }
    order.emplace_back(ver);
  }

  void rev_dfs(int ver, int now) {
    id[ver] = now;
    if (heavy) vertices[now].emplace_back(ver);
    for (int e : rev_graph[ver]) {
      if (id[e] == -1) rev_dfs(e, now);
    }
  }
};

struct UnionFind {
  UnionFind(int n) : data(n, -1) {}

  int root(int ver) { return data[ver] < 0 ? ver : data[ver] = root(data[ver]); }

  bool unite(int u, int v) {
    u = root(u);
    v = root(v);
    if (u == v) return false;
    if (data[u] > data[v]) std::swap(u, v);
    data[u] += data[v];
    data[v] = u;
    return true;
  }

  bool same(int u, int v) { return root(u) == root(v); }

  int size(int ver) { return -data[root(ver)]; }

private:
  std::vector<int> data;
};

std::vector<int> topological_sort(const std::vector<std::vector<int>> &graph) {
  int n = graph.size();
  std::vector<int> deg(n, 0);
  for (int i = 0; i < n; ++i) {
    for (int e : graph[i]) ++deg[e];
  }
  std::queue<int> que;
  for (int i = 0; i < n; ++i) {
    if (deg[i] == 0) que.emplace(i);
  }
  std::vector<int> res;
  while (!que.empty()) {
    int ver = que.front(); que.pop();
    res.emplace_back(ver);
    for (int e : graph[ver]) {
      if (--deg[e] == 0) que.emplace(e);
    }
  }
  return res.size() == n ? res : std::vector<int>();
}

int main() {
  int n, m; cin >> n >> m;
  vector<vector<int>> graph(n);
  while (m--) {
    int u, v; cin >> u >> v; --u; --v;
    graph[u].emplace_back(v);
  }
  StronglyConnectedComponents scc(graph, true);
  const int x = scc.comp.size();
  UnionFind uf(x);
  REP(i, x) for (int e : scc.comp[i]) uf.unite(i, e);
  map<int, vector<int>> root;
  REP(i, x) root[uf.root(i)].emplace_back(i);
  vector<int> ts = topological_sort(scc.comp);
  assert(!ts.empty());
  vector<int> inv(x, -1);
  REP(i, x) inv[ts[i]] = i;
  vector<int> a, b;
  for (auto [_, v] : root) {
    sort(ALL(v), [&](int l, int r) -> bool { return inv[l] < inv[r]; });
    int last = -1;
    bool need_loop = false;
    for (int e : v) {
      for (int ver : scc.vertices[e]) {
        if (last != -1) {
          a.emplace_back(last);
          b.emplace_back(ver);
        }
        last = ver;
      }
      need_loop |= scc.vertices[e].size() > 1;
    }
    if (need_loop) {
      a.emplace_back(last);
      b.emplace_back(scc.vertices[v.front()].front());
    }
  }
  int k = a.size();
  cout << k << '\n';
  REP(i, k) cout << a[i] + 1 << ' ' << b[i] + 1 << '\n';
  return 0;
}