#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  long long a[n + 1];
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  long long s = 0;
  for (int i = 1; i <= n; i++) {
    s = s ^ a[i];
  }
  if (n % 2 == 0) {
    int c = 0;
    for (int i = 1; i <= n; i++) {
      if ((s ^ a[i]) == a[i]) {
        c = i;
        break;
      }
    }
    if (c == 0) {
      cout << "NO";
    } else {
      cout << "YES" << endl;
      vector<int> k;
      for (int i = 1; i <= n; i++) {
        if (i != c) {
          k.push_back(i);
        }
      }
      cout << (n - 1) / 2 + (n - 4) / 2 << endl;
      for (int i = 2; i < n - 1; i += 2) {
        cout << k[i - 2] << " " << k[i - 1] << " " << k[i] << endl;
      }
      for (int i = 0; i < n - 4; i += 2) {
        cout << k[i] << " " << k[i + 1] << " " << k[n - 2] << endl;
      }
    }
  } else {
    cout << "YES" << endl;
    cout << (n / 2) + (n - 3) / 2 << endl;
    for (int i = 3; i <= n; i += 2) {
      cout << i - 2 << " " << i - 1 << " " << i << endl;
    }
    for (int i = 1; i < n - 3; i += 2) {
      cout << i << " " << i + 1 << " " << n << endl;
    }
  }
}
