#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
int q[N];
int n;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> q[i];
  if (n & 1) {
    cout << "YES" << '\n';
    cout << n - 1 << '\n';
    for (int i = 1; i < n; i += 2) {
      cout << i << ' ' << i + 1 << ' ' << i + 2 << '\n';
    }
    for (int i = 1; i < n; i += 2) {
      cout << i << ' ' << i + 1 << ' ' << n << '\n';
    }
  } else {
    int tmp = 0;
    for (int i = 1; i <= n; i++) tmp ^= q[i];
    if (tmp != 0) {
      cout << "NO" << '\n';
    } else {
      cout << "YES" << '\n';
      cout << n - 2 << '\n';
      for (int i = 1; i < n - 1; i += 2) {
        cout << i << ' ' << i + 1 << ' ' << i + 2 << '\n';
      }
      for (int i = 1; i < n - 1; i += 2) {
        cout << i << ' ' << i + 1 << ' ' << n - 1 << '\n';
      }
    }
  }
}
