#include <bits/stdc++.h>
using namespace std;
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
const int MAXN = 10007;
const int INF = 5000;
const int eps = 0;
struct edge {
  int a, b;
  int cap, flow;
  int yo, x, y;
};
struct Dinic {
  int s, t, d[MAXN], ptr[MAXN];
  vector<edge> e;
  vector<int> g[MAXN];
  void init() {
    e.clear();
    memset(d, 0, sizeof(d));
    for (int i = 0; i < MAXN; i++) g[i].clear();
  }
  void addEdge(int a, int b, int cap, int x = -1, int y = -1) {
    edge e1 = {a, b, cap, 0, 1, x, y};
    edge e2 = {b, a, 0, 0, 0, x, y};
    g[a].push_back((int)e.size());
    e.push_back(e1);
    g[b].push_back((int)e.size());
    e.push_back(e2);
  }
  bool bfs() {
    queue<int> Q;
    Q.push(s);
    memset(d, -1, sizeof(d));
    d[s] = 0;
    while (!Q.empty()) {
      int u = Q.front();
      Q.pop();
      for (int i = 0; i < g[u].size(); i++) {
        int id = g[u][i];
        int v = e[id].b;
        if (d[v] == -1 && e[id].flow < e[id].cap) {
          Q.push(v);
          d[v] = d[u] + 1;
        }
      }
    }
    return d[t] != -1;
  }
  int dfs(int u, int flow) {
    if (flow <= eps) return 0;
    if (u == t) return flow;
    for (int& i = ptr[u]; i < g[u].size(); i++) {
      int id = g[u][i];
      int v = e[id].b;
      if (d[v] != d[u] + 1) continue;
      int pushed = dfs(v, min(flow, e[id].cap - e[id].flow));
      if (pushed > eps) {
        e[id].flow += pushed;
        e[id ^ 1].flow -= pushed;
        return pushed;
      }
    }
    return 0;
  }
  int dinic() {
    int flow = 0;
    while (true) {
      if (!bfs()) break;
      memset(ptr, 0, sizeof(ptr));
      while (true) {
        int pushed = dfs(s, INF);
        if (pushed <= eps) break;
        flow += pushed;
      }
    }
    return flow;
  }
};
Dinic dinic0;
Dinic dinic1;
int n, m;
int X[5005];
int Y[5005];
int deg[5005];
int main() {
  scanf("%d %d", &n, &m);
  for (int i = 1; i <= m; i++) {
    int u, v;
    scanf("%d %d", &u, &v);
    X[i] = u;
    Y[i] = v;
    dinic0.addEdge(n + i, u, 1, i);
    dinic0.addEdge(n + i, v, 1, i);
    dinic0.addEdge(0, n + i, 1);
  }
  dinic0.s = 0;
  dinic0.t = n + m + 1;
  int lo = 0;
  int hi = m;
  int ans = 0;
  while (lo <= hi) {
    int mid = (lo + hi) / 2;
    dinic1 = dinic0;
    for (int i = 1; i <= n; i++) dinic1.addEdge(i, n + m + 1, mid);
    int maxflow = dinic1.dinic();
    if (maxflow >= m) {
      ans = mid;
      hi = mid - 1;
    } else
      lo = mid + 1;
  }
  cout << ans << endl;
  dinic1 = dinic0;
  for (int i = 1; i <= n; i++) dinic1.addEdge(i, n + m + 1, ans);
  int maxflow = dinic1.dinic();
  for (auto e : dinic1.e) {
    if (e.a > n && e.a < n + m + 1 && e.b >= 1 && e.b <= n && e.flow) {
      int i = e.a - n;
      if (e.b != X[i]) swap(X[i], Y[i]);
    }
  }
  for (int i = 1; i <= m; i++) {
    printf("%d %d\n", X[i], Y[i]);
    deg[X[i]]++;
  }
  for (int i = 1; i <= n; i++) assert(deg[i] <= ans);
  return 0;
}
