#include <bits/stdc++.h>
using namespace std;
struct edge {
  int from, to;
  bool bridge;
  bool straight;
};
vector<edge> edges;
vector<vector<int> > g;
vector<char> used;
vector<int> ret, tin;
int timer = 0;
void dfs1(int v, int p) {
  tin[v] = ret[v] = timer++;
  used[v] = true;
  for (int e : g[v]) {
    int to = edges[e].to;
    if (to == p) {
      continue;
    }
    if (used[to]) {
      ret[v] = min(ret[v], tin[to]);
    } else {
      dfs1(to, v);
      ret[v] = min(ret[v], ret[to]);
      if (ret[to] > tin[v]) {
        edges[e].bridge = edges[e ^ 1].bridge = true;
      }
    }
  }
}
vector<int> compId;
int dfs2(int v, int cc) {
  compId[v] = cc;
  int ans = 1;
  for (int e : g[v]) {
    if (compId[edges[e].to] != -1) {
      continue;
    }
    if (!edges[e].bridge) {
      ans += dfs2(edges[e].to, cc);
    }
  }
  return ans;
}
void dfs3(int v) {
  used[v] = true;
  for (int e : g[v]) {
    if (!edges[e].bridge) {
      if (edges[e ^ 1].straight) {
        continue;
      }
      edges[e].straight = true;
      if (!used[edges[e].to]) {
        dfs3(edges[e].to);
      }
    } else {
      if (edges[e].straight) {
        continue;
      }
      edges[e ^ 1].straight = true;
      if (!used[edges[e].to]) {
        dfs3(edges[e].to);
      }
    }
  }
}
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  g.resize(n);
  used.assign(n, false);
  ret.resize(n);
  tin.resize(n);
  for (int i = 0; i < m; ++i) {
    int u, v;
    scanf("%d%d", &u, &v);
    --u, --v;
    g[u].push_back((int)(edges).size());
    edges.push_back({u, v, false, false});
    g[v].push_back((int)(edges).size());
    edges.push_back({v, u, false, false});
  }
  dfs1(0, 0);
  compId.assign(n, -1);
  int biggestSize = -1, biggestId = -1;
  int cnt = 0;
  for (int i = 0; i < n; ++i) {
    if (compId[i] == -1) {
      int s = dfs2(i, cnt);
      if (s > biggestSize) {
        biggestSize = s;
        biggestId = i;
      }
      ++cnt;
    }
  }
  used.assign(n, false);
  dfs3(biggestId);
  printf("%d\n", biggestSize);
  for (int i = 0; i < 2 * m; ++i) {
    if (edges[i].straight) {
      printf("%d %d\n", edges[i].from + 1, edges[i].to + 1);
    }
  }
}
