#include <bits/stdc++.h>
using namespace std;
vector<vector<int> > G;
vector<bool> mark;
vector<pair<int, int> > res;
bool cycle = 0;
void dfs(int u, int p = -1) {
  mark[u] = 1;
  int i;
  for (i = 0; i < G[u].size(); i++) {
    if (!mark[G[u][i]])
      dfs(G[u][i], u);
    else if (G[u][i] != p)
      cycle = 1;
  }
}
bool check_res() {
  int i;
  for (i = 0; i < G.size(); i++)
    if (G[i].size() != 2 || !mark[i]) return 0;
  return 1;
}
bool check_good() {
  int i;
  for (i = 0; i < G.size(); i++)
    if (G[i].size() > 2) return 0;
  return 1;
}
void add() {
  int i, j;
  for (i = 0; i < G.size(); i++)
    for (j = i + 1; j < G.size(); j++)
      if (G[i].size() < 2 && G[j].size() < 2) {
        mark.assign(G.size(), 0);
        dfs(i);
        if (!mark[j]) {
          res.push_back(make_pair(i, j));
          G[i].push_back(j);
          G[j].push_back(i);
        }
      }
}
int main() {
  int n, m, i, a, b;
  cin >> n >> m;
  G.resize(n);
  mark.resize(n);
  if (n == 1) {
    if (m == 0)
      cout << "YES\n1\n1 1\n";
    else if (m == 1)
      cout << "YES\n0\n";
    else
      cout << "NO\n";
    return 0;
  }
  for (i = 0; i < m; i++) {
    cin >> a >> b;
    if (a == b) {
      cout << "NO" << endl;
      return 0;
    }
    G[a - 1].push_back(b - 1);
    G[b - 1].push_back(a - 1);
  }
  dfs(0);
  if (check_res())
    cout << "YES\n0\n";
  else if (check_good() && m <= n && !cycle) {
    cout << "YES" << endl;
    add();
    cout << res.size() + 1 << endl;
    a = -1, b = -1;
    for (i = 0; i < res.size(); i++)
      cout << res[i].first + 1 << " " << res[i].second + 1 << endl;
    for (i = 0; i < G.size(); i++)
      if (G[i].size() < 2) {
        if (a == -1)
          a = i;
        else
          b = i;
      }
    cout << a + 1 << " " << b + 1 << endl;
  } else
    cout << "NO" << endl;
  return 0;
}
