#include <bits/stdc++.h>
using namespace std;
const int N = 4e5 + 10;
struct edge {
  int u, v;
  edge(int _u, int _v) : u(_u), v(_v) {}
};
vector<edge> edges;
vector<int> E[N];
void add_edge(int u, int v) {
  E[u].push_back(edges.size());
  edges.emplace_back(u, v);
  E[v].push_back(edges.size());
  edges.emplace_back(v, u);
}
int dfn_clock, bcc_num;
int low[N], dfn[N], bcc[N], sz[N];
vector<int> stk;
void tarjan(int u, int pre) {
  stk.push_back(u);
  low[u] = dfn[u] = ++dfn_clock;
  for (auto &e : E[u]) {
    int v = edges[e].v;
    if (v == pre) continue;
    if (!dfn[v]) {
      tarjan(v, u);
      low[u] = min(low[u], low[v]);
    } else if (!bcc[v])
      low[u] = min(low[u], dfn[v]);
  }
  if (low[u] == dfn[u]) {
    ++bcc_num;
    int t;
    do {
      bcc[t = stk.back()] = bcc_num;
      sz[bcc_num]++;
      stk.pop_back();
    } while (t != u);
  }
}
vector<int> nE[N];
vector<int> ans;
bool vs[N * 2];
void solve1(int u) {
  for (auto &e : E[u]) {
    int v = edges[e].v;
    if (vs[e]) continue;
    if (bcc[v] == bcc[u]) {
      ans.push_back(e);
      vs[e] = vs[e ^ 1] = 1;
      solve1(v);
    }
  }
}
bool vs2[N];
void solve2(int u, int pre = 0) {
  for (auto &e : nE[u]) {
    int bv = bcc[edges[e].v];
    if (bv == pre) continue;
    ans.push_back(e ^ 1);
    solve2(bv, u);
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    add_edge(u, v);
  }
  for (int i = 1; i <= n; i++) {
    if (!dfn[i]) {
      tarjan(i, 0);
    }
  }
  vector<bool> vis(bcc_num + 1);
  for (int i = 1; i <= n; i++) {
    if (!vis[bcc[i]]) solve1(i), vis[bcc[i]] = 1;
  }
  for (int i = 1; i <= n; i++) {
    for (auto &e : E[i]) {
      int v = edges[e].v;
      if (bcc[i] != bcc[v]) {
        nE[bcc[i]].push_back(e);
      }
    }
  }
  int mxid = max_element(sz + 1, sz + 1 + bcc_num) - sz;
  solve2(mxid);
  sort((ans).begin(), (ans).end());
  cout << sz[mxid] << '\n';
  for (auto &e : ans) cout << edges[e].u << ' ' << edges[e].v << '\n';
  return 0;
}
