#include <bits/stdc++.h>
using namespace std;
const int MAXN = 10100;
const int INF = 1000000000;
struct edge {
  int a, b, cap, flow;
};
int n, s, t, d[MAXN], ptr[MAXN], q[MAXN];
vector<edge> e;
vector<int> g[MAXN];
void add_edge(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);
}
bool bfs() {
  int qh = 0, qt = 0;
  q[qt++] = s;
  memset(d, -1, n * sizeof d[0]);
  d[s] = 0;
  while (qh < qt && d[t] == -1) {
    int v = q[qh++];
    for (size_t 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 dinic() {
  int flow = 0;
  for (;;) {
    if (!bfs()) break;
    memset(ptr, 0, n * sizeof ptr[0]);
    while (int pushed = dfs(s, INF)) flow += pushed;
  }
  return flow;
}
int main() {
  ios::sync_with_stdio(false);
  int v, m;
  cin >> v >> m;
  s = m + v;
  t = s + 1;
  n = t + 1;
  vector<int> ed;
  for (int i = 0; i < v; i++) {
    ed.push_back(e.size());
    add_edge(i, t, 0);
  }
  map<int, pair<int, int>> wh;
  for (int i = 0; i < m; i++) {
    int a, b;
    cin >> a >> b;
    a--, b--;
    wh[e.size()] = make_pair(a, b);
    add_edge(v + i, a, 1);
    wh[e.size()] = make_pair(b, a);
    add_edge(v + i, b, 1);
    add_edge(s, v + i, 1);
  }
  int lo = 0, hi = m + 1;
  while (lo < hi) {
    int mid = (lo + hi) / 2;
    for (int i = 0; i < e.size(); i++) {
      e[i].flow = 0;
    }
    for (int id : ed) {
      e[id].cap = mid;
    }
    if (dinic() == m)
      hi = mid;
    else
      lo = mid + 1;
  }
  cout << lo << "\n";
  for (int i = 0; i < e.size(); i++) {
    e[i].flow = 0;
  }
  for (int id : ed) {
    e[id].cap = lo;
  }
  dinic();
  for (auto& p : wh) {
    if (e[p.first].flow == 1) {
      cout << p.second.first + 1 << " " << p.second.second + 1 << "\n";
    }
  }
  return 0;
}
