#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  long long n;
  cin >> n;
  long long XOR = 0;
  vector<long long> arr(n);
  for (long long i = 0; i < n; ++i) {
    cin >> arr[i];
    XOR = (XOR ^ (arr[i]));
  }
  if (n % 2 == 0 && XOR != 0) {
    cout << "NO" << '\n';
    return 0;
  }
  if (n % 2 == 0) n--;
  cout << "YES" << '\n';
  cout << n - 2 << '\n';
  for (long long i = 1; i <= n - 2; i = i + 2)
    cout << i << " " << i + 1 << " " << i + 2 << '\n';
  for (long long i = n - 2; i >= 3; i = i - 2)
    cout << i << " " << i - 1 << " " << i - 2 << '\n';
  return 0;
}
