#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  while (t--) {
    long long n;
    cin >> n;
    long long a[n + 1];
    long long xor_v = 0;
    for (long long i = 1; i <= n; i++) {
      cin >> a[i];
      xor_v = xor_v ^ a[i];
    }
    if (n % 2 == 0 && xor_v != 0) {
      cout << "NO"
           << "\n";
    } else {
      if (n % 2 == 0) n--;
      cout << "YES"
           << "\n";
      vector<vector<long long> > ans;
      ans.push_back({1, 2, 3});
      for (long long i = 4; i <= n - 1; i += 2) {
        ans.push_back({i - 1, i, i + 1});
      }
      for (long long i = 1; i <= n - 3; i += 2) {
        ans.push_back({i, i + 1, n});
      }
      cout << ans.size() << "\n";
      for (auto v : ans) {
        cout << v[0] << " " << v[1] << " " << v[2] << "\n";
      }
    }
  }
  return 0;
}
