#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  long long int n;
  cin >> n;
  long long int a[n];
  long long int x = 0;
  for (long long int i = 0; i < n; i++) {
    cin >> a[i];
    x ^= a[i];
  }
  if (x != 0 && n % 2 == 0)
    cout << "NO"
         << "\n";
  else {
    cout << "YES"
         << "\n";
    vector<pair<pair<long long int, long long int>, long long int>> vp;
    for (long long int i = 0; i < n - 2; i += 2) {
      vp.push_back({{i + 1, i + 2}, i + 3});
    }
    if (n % 2 == 0) {
      for (long long int i = n - 4; i >= 2; i -= 2) {
        vp.push_back({{i + 1, i}, i - 1});
      }
    } else {
      for (long long int i = n - 3; i >= 2; i -= 2) {
        vp.push_back({{i + 1, i}, i - 1});
      }
    }
    cout << vp.size() << "\n";
    for (auto x : vp) {
      cout << x.first.first << " " << x.first.second << " " << x.second << "\n";
    }
  }
  return 0;
}
