#include <bits/stdc++.h>
using namespace std;
static const int INF = 0x3f3f3f3f;
static const long long INFL = 0x3f3f3f3f3f3f3f3fLL;
template <typename T, typename U>
static void amin(T &x, U y) {
  if (y < x) x = y;
}
template <typename T, typename U>
static void amax(T &x, U y) {
  if (x < y) x = y;
}
struct MaximumFlow {
  static const int InfCapacity = INF;
  struct Edge {
    int to;
    int capacity;
    int rev;
  };
  vector<vector<Edge>> g;
  void init(int n) { g.assign(n, vector<Edge>()); }
  void add(int i, int j, int capacity) {
    Edge e, f;
    e.to = j, f.to = i;
    e.capacity = capacity, f.capacity = 0;
    g[i].push_back(e);
    g[j].push_back(f);
    g[i].back().rev = (int)g[j].size() - 1;
    g[j].back().rev = (int)g[i].size() - 1;
  }
  void addB(int i, int j, int capacity) {
    Edge e, f;
    e.to = j, f.to = i;
    e.capacity = capacity, f.capacity = capacity;
    g[i].push_back(e);
    g[j].push_back(f);
    g[i].back().rev = (int)g[j].size() - 1;
    g[j].back().rev = (int)g[i].size() - 1;
  }
  int maximumFlow(int s, int t) {
    int n = g.size();
    vector<int> level(n);
    int total = 0;
    bool update;
    do {
      update = false;
      fill(level.begin(), level.end(), -1);
      level[s] = 0;
      queue<int> q;
      q.push(s);
      for (int d = n; !q.empty() && level[q.front()] < d;) {
        int u = q.front();
        q.pop();
        if (u == t) d = level[u];
        for (auto e = (g[u]).begin(); e != (g[u]).end(); ++e)
          if (e->capacity > 0 && level[e->to] == -1)
            q.push(e->to), level[e->to] = level[u] + 1;
      }
      vector<int> iter(n);
      for (int i = 0; i < n; i++) iter[i] = (int)g[i].size() - 1;
      while (1) {
        int f = augment(level, iter, s, t, InfCapacity);
        if (f == 0) break;
        total += f;
        update = true;
      }
    } while (update);
    return total;
  }
  int augment(vector<int> &level, vector<int> &iter, int u, int t, int f) {
    if (u == t || f == 0) return f;
    int lv = level[u];
    if (lv == -1) return 0;
    level[u] = -1;
    for (; iter[u] >= 0; --iter[u]) {
      Edge &e = g[u][iter[u]];
      if (level[e.to] <= lv) continue;
      int l = augment(level, iter, e.to, t, min(f, e.capacity));
      if (l == 0) continue;
      e.capacity -= l;
      g[e.to][e.rev].capacity += l;
      level[u] = lv;
      return l;
    }
    return 0;
  }
};
int main() {
  int n;
  int m;
  while (~scanf("%d%d", &n, &m)) {
    vector<array<int, 2>> edges(m);
    for (int(i) = 0; (i) < (int)(m); ++(i)) {
      int x;
      int y;
      scanf("%d%d", &x, &y), --x, --y;
      edges[i] = {x, y};
    }
    vector<pair<int, int>> ans(m);
    int lo = 0, up = m + 1;
    while (up - lo > 0) {
      int mid = (lo + up) / 2;
      MaximumFlow mf;
      int src = m + n, dst = src + 1;
      mf.init(dst + 1);
      for (int(i) = 0; (i) < (int)(m); ++(i)) mf.add(src, i, 1);
      for (int(i) = 0; (i) < (int)(m); ++(i))
        for (int j : edges[i]) mf.add(i, m + j, 1);
      for (int(j) = 0; (j) < (int)(n); ++(j)) mf.add(m + j, dst, mid);
      int f = mf.maximumFlow(src, dst);
      if (f == m) {
        up = mid;
        for (int(i) = 0; (i) < (int)(m); ++(i)) {
          for (auto e : mf.g[i])
            if (e.capacity == 0 && m <= e.to && e.to < m + n) {
              int x = e.to - m;
              auto p = make_pair(edges[i][0], edges[i][1]);
              if (p.first != x) swap(p.first, p.second);
              ans[i] = p;
            }
        }
      } else {
        lo = mid + 1;
      }
    }
    printf("%d\n", up);
    for (int i = 0; i < (int)ans.size(); ++i)
      printf("%d %d\n", ans[i].first + 1, ans[i].second + 1);
  }
  return 0;
}
