#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 500;
int n;
long long a[maxn], ans;
int main() {
  cin.tie(0);
  cout.tie(0);
  ios_base::sync_with_stdio(false);
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  for (int i = 1; i <= n; i++) {
    ans ^= a[i];
  }
  if (n % 2 == 0 && ans != 0) {
    cout << "NO" << endl;
  } else if (n % 2 == 1) {
    cout << "YES" << endl;
    cout << n - 1 << endl;
    for (int i = 1; i <= (n - 1) / 2; i++) {
      cout << 2 * (i - 1) + 1 << " " << 2 * (i - 1) + 2 << " "
           << 2 * (i - 1) + 3 << endl;
    }
    for (int i = 1; i <= (n - 1) / 2; i++) {
      cout << 2 * (i - 1) + 1 << " " << 2 * (i - 1) + 2 << " " << n << endl;
    }
  } else if (n % 2 == 0) {
    cout << "YES" << endl;
    cout << (n - 1) - 1 << endl;
    for (int i = 1; i <= (n - 2) / 2; i++) {
      cout << 2 * (i - 1) + 1 << " " << 2 * (i - 1) + 2 << " "
           << 2 * (i - 1) + 3 << endl;
    }
    for (int i = 1; i <= (n - 2) / 2; i++) {
      cout << 2 * (i - 1) + 1 << " " << 2 * (i - 1) + 2 << " " << n - 1 << endl;
    }
  }
  return 0;
}
