#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1e9 + 7;
const long long int inf = 1e18;
vector<long long int> fact;
long long int mpow(long long int base, long long int exp);
bool isPrime(long long int num);
bool isPowerTwo(long long int x);
bool isSubstring(string s1, string s2);
void factorial(long long int num);
void factmod(long long int num);
void primeFactor(long long int num);
void itzprasuk() {
  long long int n, m, m1;
  cin >> n >> m;
  m1 = m;
  long long int p, q;
  vector<long long int> cnt(n + 1, 0);
  vector<pair<long long int, long long int> > v;
  while (m1--) {
    cin >> p >> q;
    v.push_back(make_pair(p, q));
    cnt[p]++;
    cnt[q]++;
  }
  long long int g;
  for (long long int i = 1; i < n + 1; i++) {
    if (cnt[i] == 0) {
      g = i;
      break;
    }
  }
  cout << n - 1 << "\n";
  for (long long int i = 0; i < m; i++) {
    if (cnt[v[i].first] != -1) {
      cout << v[i].first << " " << g << "\n";
      cnt[v[i].first] = -1;
    }
    if (cnt[v[i].second] != -1) {
      cout << g << " " << v[i].second << "\n";
      cnt[v[i].second] = -1;
    }
  }
  for (long long int i = 1; i < n + 1; i++) {
    if (i != g && cnt[i] == 0) {
      cout << g << " " << i << "\n";
    }
  }
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int T = clock();
  long long int t = 1;
  while (t--) {
    itzprasuk();
  }
  cerr << "TIME : " << 1000 * (double)(clock() - T) / CLOCKS_PER_SEC << " ms\n";
  T = clock();
  return 0;
}
long long int mpow(long long int base, long long int exp) {
  base %= mod;
  long long int result = 1;
  while (exp > 0) {
    if (exp & 1) result = ((long long int)result * base) % mod;
    base = ((long long int)base * base) % mod;
    exp >>= 1;
  }
  return result;
}
bool isPrime(long long int num) {
  if (num <= 1) return false;
  for (long long int i = 2; i * i <= num; i++)
    if (num % i == 0) return false;
  return true;
}
bool isPowerTwo(long long int x) { return (x && !(x & (x - 1))); }
bool isSubstring(string s1, string s2) {
  if (s1.find(s2) != string::npos)
    return true;
  else
    return false;
}
void factorial(long long int num) {
  fact[0] = 1;
  for (long long int i = 1; i <= num; i++) fact[i] = i * fact[i - 1];
}
void factmod(long long int num) {
  fact[0] = 1;
  for (long long int i = 1; i <= num; i++) fact[i] = (i * fact[i - 1]) % mod;
}
void primeFactor(long long int num) {
  for (long long int i = 2; i <= num; i++)
    if (num % i == 0) {
      long long int cnt = 0;
      while (num % i == 0) cnt++, num /= i;
      cout << i << "^" << cnt << " ";
    }
  if (num > 1)
    cout << num << "^"
         << "1"
         << " ";
}
