#include <bits/stdc++.h>
using namespace std;
template <class T>
void smin(T &a, T b) {
  a = min(a, b);
}
template <class T>
void smax(T &a, T b) {
  a = max(a, b);
}
template <class T>
void print(vector<T> &a, string sep) {
  for (T el : a) cout << el << sep;
  cout << endl;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  vector<long long> a(n);
  for (int i = 0; i < n; ++i) cin >> a[i];
  ;
  long long x = a[0] ^ a[1];
  for (int i = 2; i < n; i++) {
    x ^= a[i];
  }
  int final = n - 1;
  if (n % 2 == 0) {
    if (x != 0) {
      cout << "NO" << endl;
      return 0;
    }
    final = n - 2;
  }
  vector<tuple<int, int, int>> ops;
  for (int i = 0; i < final - 1; i += 2) {
    ops.push_back(make_tuple(i, i + 1, i + 2));
  }
  for (int i = 0; i < final - 1; i += 2) {
    ops.push_back(make_tuple(final, i, i + 1));
  }
  cout << "YES" << endl;
  cout << ops.size() << endl;
  for (auto el : ops) {
    cout << get<0>(el) + 1 << " " << get<1>(el) + 1 << " " << get<2>(el) + 1
         << endl;
  }
}
