#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int arr[n];
  int xori = 0;
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
    xori ^= arr[i];
  }
  if (n % 2 == 0 && xori != 0) {
    cout << "NO" << endl;
    return 0;
  }
  cout << "YES" << endl;
  if (n & 1) {
    cout << (n - 1) << endl;
    for (int i = 0; i <= n - 3; i += 2) {
      cout << i + 1 << " " << i + 2 << " " << i + 3 << endl;
    }
    for (int i = 0; i <= n - 3; i += 2) {
      cout << i + 1 << " " << i + 2 << " " << n << endl;
    }
  } else {
    cout << (n - 2) << endl;
    for (int i = 0; i <= n - 3; i += 2) {
      cout << i + 1 << " " << i + 2 << " " << i + 3 << endl;
    }
    for (int i = 0; i <= n - 3; i += 2) {
      cout << i + 1 << " " << i + 2 << " " << n - 1 << endl;
    }
  }
}
