#include <bits/stdc++.h>
using namespace std;
long double PI = 3.14159265359;
long long inf = 1000000000000000007;
long long mod = 1000000007;
long long mod1 = 998244353;
const bool multi = 0;
long long tab[100007];
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long tt;
  if (multi)
    cin >> tt;
  else
    tt = 1;
  while (tt--) {
    long long n, x = 0;
    cin >> n;
    for (long long i = 1; i <= n; i++) {
      cin >> tab[i];
      x ^= tab[i];
    }
    if (n % 2 == 0 && x != 0)
      cout << "NO";
    else {
      cout << "YES" << '\n';
      cout << n - 2 - (n % 2 == 0) << '\n';
      for (long long i = 3; i <= n; i += 2)
        cout << i - 2 << " " << i - 1 << " " << i << '\n';
      for (long long i = 2; i <= n - 3; i += 2)
        cout << i - 1 << " " << i << " " << n << '\n';
    }
  }
  return 0;
}
