#include <bits/stdc++.h>
using namespace std;
int used[100];
vector<vector<int>> g;
int cmp = 0;
vector<int> parent, rank1;
void make_set(int v) {
  parent[v] = v;
  rank1[v] = 0;
}
int find_set(int v) {
  if (v == parent[v]) return v;
  return parent[v] = find_set(parent[v]);
}
void union_sets(int a, int b) {
  a = find_set(a);
  b = find_set(b);
  if (a != b) {
    if (rank1[a] < rank1[b]) swap(a, b);
    parent[b] = a;
    if (rank1[a] == rank1[b]) ++rank1[a];
  }
}
bool ok = 1;
void dfs(int v, int p = -1) {
  used[v] = 1;
  for (auto to : g[v]) {
    if (!used[to])
      union_sets(v, to), dfs(to, v);
    else {
      if (to != p) ok = 0;
    }
  }
}
signed main() {
  ios_base::sync_with_stdio(0), cin.tie(0);
  int n, m;
  cin >> n >> m;
  parent.resize(n);
  rank1.resize(n);
  for (int i = 0; i < n; ++i) make_set(i);
  g.resize(n);
  bool ok1 = 1, ok2 = 1, ok3 = 1;
  bool ok4 = 1;
  if (m > n) ok1 = 0;
  for (int i = 0; i < m; ++i) {
    int a, b;
    cin >> a >> b;
    a--, b--;
    g[a].push_back(b);
    g[b].push_back(a);
    if (g[a].size() > 2 || g[b].size() > 2) {
      ok2 = 0;
    }
  }
  dfs(0);
  for (int i = 0; i < n; ++i) {
    if (!used[i]) ok3 = 0;
    if (g[i].size() != 2) ok4 = 0;
  }
  if (ok4 && ok3) {
    cout << "YES" << endl << 0;
    return 0;
  }
  memset(used, 0, sizeof(used));
  for (int i = 0; i < n; ++i) {
    if (!used[i]) dfs(i);
  }
  if (!(ok1 && ok2 && ok)) {
    cout << "NO";
    return 0;
  }
  vector<pair<int, int>> ans;
  vector<int> cur;
  vector<int> deg(n);
  for (int i = 0; i < n; ++i) {
    deg[i] = g[i].size();
    if (deg[i] <= 1) cur.push_back(i);
  }
  for (int i = 0; i < n; ++i) {
    if (!used[i]) {
      dfs(i);
      cmp++;
    }
  }
  vector<int> nd;
  for (int i = 0; i < n; ++i) {
    for (int j = i + 1; j < n; ++j) {
      if (deg[i] >= 2 || deg[j] >= 2) continue;
      if (find_set(i) != find_set(j)) {
        ans.push_back({i, j});
        deg[i]++;
        deg[j]++;
        union_sets(i, j);
      }
    }
  }
  for (int i = 0; i < n; ++i) {
    if (deg[i] <= 1) nd.push_back(i);
  }
  ans.push_back({nd[0], nd[nd.size() - 1]});
  cout << "YES\n" << ans.size() << '\n';
  for (auto u : ans) cout << u.first + 1 << ' ' << u.second + 1 << '\n';
  return 0;
}
