#include <bits/stdc++.h>
using namespace std;
const int INF = 1000000000;
struct Edge {
  int a, b, cap, flow;
};
struct MaxFlow {
  int n, s, t;
  vector<int> d, ptr, q;
  vector<Edge> e;
  vector<vector<int> > g;
  MaxFlow(int n) : n(n), d(n), ptr(n), q(n), g(n) {
    e.clear();
    for (int i = 0; i < n; ++i) {
      g[i].clear();
      ptr[i] = 0;
    }
  }
  void addEdge(int a, int b, int cap) {
    Edge e1 = {a, b, cap, 0};
    Edge e2 = {b, a, 0, 0};
    g[a].push_back((int)e.size());
    e.push_back(e1);
    g[b].push_back((int)e.size());
    e.push_back(e2);
  }
  void reset(int limit, int t) {
    for (auto &ed : e) {
      ed.flow = 0;
      if (ed.b == t) ed.cap = limit;
    }
  }
  int getMaxFlow(int _s, int _t) {
    s = _s;
    t = _t;
    int flow = 0;
    for (;;) {
      if (!bfs()) break;
      for (int i = 0; i < n; ++i) ptr[i] = 0;
      while (int pushed = dfs(s, INF)) flow += pushed;
    }
    return flow;
  }

 private:
  bool bfs() {
    int qh = 0, qt = 0;
    q[qt++] = s;
    for (int i = 0; i < n; ++i) d[i] = -1;
    d[s] = 0;
    while (qh < qt && d[t] == -1) {
      int v = q[qh++];
      for (int i = 0; i < g[v].size(); ++i) {
        int id = g[v][i], to = e[id].b;
        if (d[to] == -1 && e[id].flow < e[id].cap) {
          q[qt++] = to;
          d[to] = d[v] + 1;
        }
      }
    }
    return d[t] != -1;
  }
  int dfs(int v, int flow) {
    if (!flow) return 0;
    if (v == t) return flow;
    for (; ptr[v] < (int)g[v].size(); ++ptr[v]) {
      int id = g[v][ptr[v]], to = e[id].b;
      if (d[to] != d[v] + 1) continue;
      int pushed = dfs(to, min(flow, e[id].cap - e[id].flow));
      if (pushed) {
        e[id].flow += pushed;
        e[id ^ 1].flow -= pushed;
        return pushed;
      }
    }
    return 0;
  }
};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, m;
  cin >> n >> m;
  vector<pair<int, int> > edges;
  vector<int> ans(m);
  int s = 0, t = n + m + 1;
  MaxFlow flow(t + 1);
  for (int i = 1; i <= m; ++i) {
    int u, v;
    cin >> u >> v;
    edges.push_back({u, v});
    flow.addEdge(i + n, u, 1);
    flow.addEdge(i + n, v, 1);
    flow.addEdge(s, i + n, 1);
  }
  for (int i = 1; i <= n; ++i) flow.addEdge(i, t, 0);
  int res = n - 1;
  int l = 0, r = n - 2;
  while (l <= r) {
    int mid = (l + r) >> 1;
    flow.reset(mid, t);
    if (flow.getMaxFlow(s, t) == m)
      res = mid, r = mid - 1;
    else
      l = mid + 1;
  }
  flow.reset(res, t);
  flow.getMaxFlow(s, t);
  cout << res << '\n';
  for (auto [a, b, cap, flow] : flow.e)
    if (n < a && a <= n + m && 1 <= b && b <= n && flow > 0) ans[a - n - 1] = b;
  for (int i = 0; i < m; ++i)
    cout << ans[i] << ' ' << edges[i].first + edges[i].second - ans[i] << '\n';
  return 0;
}
