#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, i, j, x, y;
  bool B[1005];
  cin >> n >> m;
  for (i = 0; i < n; i++) B[i] = true;
  for (i = 0; i < m; i++) {
    cin >> x >> y;
    B[x - 1] = false;
    B[y - 1] = false;
  }
  for (i = 0; i < n; i++)
    if (B[i]) break;
  cout << n - 1 << endl;
  for (j = 0; j < n; j++) {
    if (j == i) continue;
    cout << j + 1 << " " << i + 1 << endl;
  }
  return 0;
}
