#include <bits/stdc++.h>
using namespace std;
const long long maxn = 1e5 + 5;
long long solve() {
  long long n, sum = 0, a;
  cin >> n;
  for (long long i = 1; i <= n; ++i) cin >> a, sum ^= a;
  if (n % 2 == 0) {
    if (sum) return cout << "NO\n", 0;
    n--;
  }
  cout << "YES\n" << n - 1 << "\n";
  for (long long i = 1; i < n; i += 2)
    cout << i << " " << i + 1 << " " << i + 2 << "\n";
  for (long long i = 1; i < n; i += 2)
    cout << i << " " << i + 1 << " " << n << "\n";
}
signed main() {
  long long _ = 1;
  while (_--) {
    solve();
  }
  return 0;
}
