#include <bits/stdc++.h>
using namespace std;
bool helper(pair<int, int>* arr, int x, int y, int m) {
  if (m == 0) {
    return true;
  }
  int res = false;
  if (x != -1) {
    if (arr->first == x || arr->second == x) res = true;
  }
  if (y != -1) {
    if (arr->second == y || arr->first == y) res = true;
  }
  if (!res) {
    if (x == -1) {
      return helper(arr + 1, arr->first, y, m - 1) ||
             helper(arr + 1, arr->second, y, m - 1);
    }
    if (y == -1) {
      return helper(arr + 1, x, arr->second, m - 1) ||
             helper(arr + 1, x, arr->first, m - 1);
    }
    return false;
  }
  return helper(arr + 1, x, y, m - 1);
}
int main() {
  int n, m;
  cin >> n >> m;
  pair<int, int> arr[m];
  for (int i = 0; i < m; i++) {
    cin >> arr[i].first >> arr[i].second;
  }
  if (helper(arr, -1, -1, m)) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }
  return 0;
}
