#include <bits/stdc++.h>
struct Edge {
  Edge(int a, int b) {
    to = a;
    cap = b;
  }
  int to, cap;
};
class Dinic {
 public:
  Dinic(int n) {
    edges.resize(n);
    this->n = n;
  }
  int maxFlow(int src, int sink) {
    int ans = 0;
    while (bfs(src, sink)) {
      int flow;
      pt.assign(n, 0);
      while (flow = dfs(src, sink)) ans += flow;
    }
    return ans;
  }
  void addEdge(int from, int to, int cap) {
    edges[from].push_back(list.size());
    list.push_back(Edge(to, cap));
    edges[to].push_back(list.size());
    list.push_back(Edge(from, 0));
  }
  std::vector<int> getEdges() {
    std::vector<int> ans;
    for (int i = 0; i < list.size(); i += 2) {
      if (list[i].cap == 0) ans.push_back(i / 2);
    }
    return ans;
  }

 private:
  int n;
  std::vector<std::vector<int> > edges;
  std::vector<Edge> list;
  std::vector<int> h, pt;
  int dfs(int on, int sink, int flow = 1e9) {
    if (flow == 0) return 0;
    if (on == sink) return flow;
    for (; pt[on] < edges[on].size(); pt[on]++) {
      int cur = edges[on][pt[on]];
      if (h[on] + 1 != h[list[cur].to]) continue;
      int got = dfs(list[cur].to, sink, std::min(flow, list[cur].cap));
      if (got) {
        list[cur].cap -= got;
        list[cur ^ 1].cap += got;
        return got;
      }
    }
    return 0;
  }
  bool bfs(int src, int sink) {
    h.assign(n, n + 10);
    h[src] = 0;
    std::queue<int> q;
    q.push(src);
    while (!q.empty()) {
      int on = q.front();
      q.pop();
      for (auto a : edges[on]) {
        if (list[a].cap == 0) continue;
        int to = list[a].to;
        if (h[to] > h[on] + 1) {
          h[to] = h[on] + 1;
          q.push(to);
        }
      }
    }
    return h[sink] <= n;
  }
};
bool can(int n, int m, Dinic graph, int x) {
  for (int i = 0; i < n; i++) graph.addEdge(i, n + m + 1, x);
  return graph.maxFlow(n + m, n + m + 1) == m;
}
int main() {
  int n, m;
  std::cin >> n >> m;
  int src = n + m;
  int sink = src + 1;
  Dinic graph(n + m + 2);
  std::vector<std::pair<int, int> > hmm;
  for (int i = 0; i < m; i++) {
    int u, v;
    std::cin >> u >> v;
    hmm.emplace_back(u, v);
    u--;
    v--;
    graph.addEdge(src, n + i, 1);
    graph.addEdge(n + i, u, 1);
    graph.addEdge(n + i, v, 1);
  }
  int l = 0, r = m;
  while (l != r) {
    int mid = (l + r) / 2;
    if (can(n, m, graph, mid))
      r = mid;
    else
      l = mid + 1;
  }
  for (int i = 0; i < n; i++) graph.addEdge(i, sink, l);
  graph.maxFlow(src, sink);
  std::vector<int> edges = graph.getEdges();
  std::cout << l << '\n';
  for (auto a : edges) {
    if (a < 3 * m) {
      if (a % 3 == 1)
        std::cout << hmm[a / 3].first << ' ' << hmm[a / 3].second << '\n';
      else if (a % 3 == 2)
        std::cout << hmm[a / 3].second << ' ' << hmm[a / 3].first << '\n';
    }
  }
}
