#include <bits/stdc++.h>
using namespace std;
void solve() {
  int n;
  cin >> n;
  long long int arr[n];
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }
  if (n % 2 == 0) {
    long long int x = 0;
    for (int i = 0; i < n; i++) {
      x = x ^ arr[i];
    }
    if (x != 0) {
      cout << "NO\n";
      return;
    }
  }
  cout << "YES\n";
  int times = (n - 1) / 2;
  cout << 2 * times << endl;
  for (int i = 0; i < times; i++) {
    cout << 2 * i + 1 << " " << 2 * i + 2 << " " << n << endl;
  }
  for (int i = 0; i < times; i++) {
    cout << 2 * i + 1 << " " << 2 * i + 2 << " " << n << endl;
  }
}
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;
  for (int i = 0; i < t; i++) {
    solve();
  }
}
