#include <bits/stdc++.h>
using namespace std;
void bam(vector<int> a, int n) {
  vector<vector<int>> answer;
  for (int i = 0; i + 2 < n; i += 2) {
    vector<int> x = {i, i + 1, i + 2};
    answer.push_back(x);
  }
  for (int i = 0; i + 2 < n; i += 2) {
    vector<int> x = {n - 1, i, i + 1};
    answer.push_back(x);
  }
  cout << "YES\n";
  cout << answer.size() << "\n";
  for (int i = 0; i < (int)answer.size(); i++) {
    cout << answer[i][0] + 1 << " " << answer[i][1] + 1 << " "
         << answer[i][2] + 1 << "\n";
  }
}
void solve() {
  int n, x;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    cin >> x;
    a[i] = x;
  }
  if (n % 2) {
    bam(a, n);
  } else {
    int x = 0;
    for (int i = 0; i < n; i++) {
      x ^= a[i];
    }
    if (x == 0) {
      bam(a, n - 1);
    } else {
      cout << "NO\n";
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int tt = 1;
  while (tt--) {
    solve();
  }
}
