#include <bits/stdc++.h>
using namespace std;
bool imp = false;
void solve() {
  long long n = 0, m = 0, i = 0, j = 0, k = 0, c = 0, flag = 0, sum = 0;
  string s, t;
  cin >> n;
  long long a[n + 5];
  for (i = 0; i < n; i++) {
    cin >> a[i];
    k ^= a[i];
  }
  if (n % 2 == 0 and k) {
    cout << "NO\n";
    return;
  }
  cout << "YES\n";
  vector<vector<long long>> v;
  if (!(n & 1)) n--;
  for (i = 0; i < n - 2; i += 2) {
    v.push_back({i, i + 1, i + 2});
  }
  for (i = 0; i < n - 2; i += 2) {
    v.push_back({i, i + 1, n - 1});
  }
  cout << v.size() << '\n';
  for (auto it : v) {
    for (auto itt : it) cout << itt + 1 << " ";
    cout << '\n';
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t = 1;
  if (imp) cin >> t;
  long long j = t;
  while (t--) {
    solve();
  }
  return 0;
}
