#include <bits/stdc++.h>
using namespace std;
const int maxnodes = 10007;
int nodes = maxnodes, src, dest, lastnode = 5000, SRC, SINK;
int dist[maxnodes], q[maxnodes], work[maxnodes], give[maxnodes];
pair<int, int> rel[maxnodes / 2], res[maxnodes / 2];
struct Edge {
  int to, rev;
  int f, cap;
};
vector<Edge> g[maxnodes];
void clearr() {
  for (int i = 0; i < maxnodes; i++) g[i].clear();
}
void addEdge(int s, int t, int cap) {
  Edge a = {t, (int)g[t].size(), 0, cap};
  Edge b = {s, (int)g[s].size(), 0, 0};
  g[s].push_back(a);
  g[t].push_back(b);
}
bool dinic_bfs(int src, int dest) {
  memset(dist, -1, sizeof dist);
  dist[src] = 0;
  queue<int> q;
  q.push(src);
  while (!q.empty()) {
    int u = q.front();
    q.pop();
    for (int j = 0; j < g[u].size(); j++) {
      Edge &e = g[u][j];
      if (dist[e.to] < 0 && e.f < e.cap) {
        dist[e.to] = dist[u] + 1;
        q.push(e.to);
      }
    }
  }
  return dist[dest] >= 0;
}
int dinic_dfs(int u, int f) {
  if (u == dest) return f;
  for (int &i = work[u]; i < (int)g[u].size(); i++) {
    Edge &e = g[u][i];
    if (e.cap <= e.f) continue;
    int v = e.to;
    if (dist[v] == dist[u] + 1) {
      int df = dinic_dfs(v, min(f, e.cap - e.f));
      if (df > 0) {
        e.f += df;
        g[v][e.rev].f -= df;
        return df;
      }
    }
  }
  return 0;
}
int maxFlow(int _src, int _dest) {
  src = _src;
  dest = _dest;
  int result = 0;
  while (dinic_bfs(src, dest)) {
    fill(work, work + nodes, 0);
    while (int delta = dinic_dfs(src, INT_MAX)) {
      result += delta;
    }
  }
  return result;
}
int f(int mid, int n, int m) {
  SRC = 0, SINK = 10001;
  for (int i = 1; i <= m; i++) addEdge(SRC, i, 1);
  for (int i = 1; i <= n; i++) addEdge(i + lastnode, SINK, mid);
  for (int i = 1; i <= m; i++) {
    int u = rel[i].first;
    int v = rel[i].second;
    addEdge(i, u + lastnode, 1);
    addEdge(i, v + lastnode, 1);
  }
  int flow = maxFlow(SRC, SINK);
  return flow;
}
int main() {
  int n, m, u, v;
  cin >> n >> m;
  for (int i = 1; i <= m; i++) {
    cin >> u >> v;
    rel[i] = {u, v};
  }
  int low = 0, high = 5009, mid;
  int cnt = 0;
  while (cnt++ < 32) {
    mid = low + (high - low) / 2;
    int flow = f(mid, n, m);
    if (flow < m)
      low = mid;
    else
      high = mid;
    clearr();
  }
  if (f(mid, n, m) < m) mid++;
  clearr();
  f(mid, n, m);
  for (int i = 1; i <= m; i++) {
    Edge e1 = g[i][1];
    e1.to -= lastnode;
    Edge e2 = g[i][2];
    e2.to -= lastnode;
    if (e1.f == e1.cap) {
      give[e1.to]++;
      res[i] = {e1.to, e2.to};
    } else if (e2.f == e2.cap) {
      give[e2.to]++;
      res[i] = {e2.to, e1.to};
    }
  }
  int mn = 10000000, mx = 0;
  for (int i = 1; i <= n; i++) {
    mx = max(mx, give[i]);
    mn = min(mn, give[i]);
  }
  cout << mx << endl;
  for (int i = 1; i <= m; i++) printf("%d %d\n", res[i].first, res[i].second);
}
