#include <bits/stdc++.h>
using namespace std;
int nn, mm;
struct Dinic {
  struct edge {
    int to, flow, cap;
  };
  const static int N = 20007;
  vector<edge> e;
  vector<int> g[N + 7];
  int dp[N + 7];
  int ptr[N + 7];
  void clear() {
    for (int i = 0; i < N + 7; i++) g[i].clear();
    e.clear();
  }
  void addEdge(int a, int b, int cap) {
    g[a].push_back(e.size());
    e.push_back({b, 0, cap});
    g[b].push_back(e.size());
    e.push_back({a, 0, 0});
  }
  int minFlow, start, finish;
  bool bfs() {
    for (int i = 0; i < N; i++) dp[i] = -1;
    dp[start] = 0;
    vector<int> st;
    int uk = 0;
    st.push_back(start);
    while (uk < st.size()) {
      int v = st[uk++];
      for (int to : g[v]) {
        auto ed = e[to];
        if (ed.cap - ed.flow >= minFlow && dp[ed.to] == -1) {
          dp[ed.to] = dp[v] + 1;
          st.push_back(ed.to);
        }
      }
    }
    return dp[finish] != -1;
  }
  int dfs(int v, int flow) {
    if (v == finish) return flow;
    for (; ptr[v] < g[v].size(); ptr[v]++) {
      int to = g[v][ptr[v]];
      edge ed = e[to];
      if (ed.cap - ed.flow >= minFlow && dp[ed.to] == dp[v] + 1) {
        int add = dfs(ed.to, min(flow, ed.cap - ed.flow));
        if (add) {
          e[to].flow += add;
          e[to ^ 1].flow -= add;
          return add;
        }
      }
    }
    return 0;
  }
  int dinic(int start, int finish) {
    Dinic::start = start;
    Dinic::finish = finish;
    int flow = 0;
    for (minFlow = (1 << 30); minFlow; minFlow >>= 1) {
      while (bfs()) {
        for (int i = 0; i < N; i++) ptr[i] = 0;
        while (int now = dfs(start, (int)2e9 + 7)) flow += now;
      }
    }
    return flow;
  }
} dinic;
pair<int, int> aa[5555];
bool can(int val) {
  dinic.clear();
  for (int i = 0; i < nn; i++) {
    dinic.addEdge(nn + mm, i, val);
  }
  for (int i = 0; i < mm; i++) {
    dinic.addEdge(nn + i, nn + mm + 1, 1);
  }
  for (int i = 0; i < mm; i++) {
    dinic.addEdge(aa[i].first, nn + i, 1);
    dinic.addEdge(aa[i].second, nn + i, 1);
  }
  int ans = dinic.dinic(nn + mm, nn + mm + 1);
  return ans == mm;
}
int main() {
  cin >> nn >> mm;
  for (int i = 0; i < mm; i++) cin >> aa[i].first >> aa[i].second;
  for (int i = 0; i < mm; i++) aa[i].first--, aa[i].second--;
  int vl = 0, vr = mm;
  while (vl + 1 < vr) {
    int vm = (vl + vr) >> 1;
    if (can(vm))
      vr = vm;
    else
      vl = vm;
  }
  cout << vr << "\n";
  can(vr);
  for (int i = 0; i < nn; i++) {
    for (int to : dinic.g[i]) {
      if (dinic.e[to].flow == 1) {
        cout << i + 1 << ' '
             << aa[dinic.e[to].to - nn].first + aa[dinic.e[to].to - nn].second -
                    i + 1
             << "\n";
      }
    }
  }
}
