#include <iostream>
#include <vector>

using namespace std;

bool g[500][500];

int main() {
  int n, m;
  cin >> n >> m;

  vector<int> deg(n);
  for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    deg[u]++;
    deg[v]++;
    g[u][v] = true;
    g[v][u] = true;
  }
  for (int i = 0; i < n; i++) g[i][i] = true;
  for (int k = 0; k < n; k++) for (int i = 0; i < n; i++) for (int j = 0; j < n; j++) g[i][j] |= g[i][k] && g[k][j];

  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (deg[i] > 0 && deg[j] > 0 && !g[i][j]) {
        cout << "NO" << endl;
        return 0;
      }
    }
  }

  int odd = 0;
  int even = 0;
  for (int i = 0; i < n; i++) {
    even += deg[i] % 2 == 0;
    odd += deg[i] % 2 == 1;
  }
  
  if (odd == 0 || odd == 2) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }
}