#include <bits/stdc++.h>
using namespace std;
bool pr[10000005] = {false};
vector<long long> prime;
void prim() {
  pr[0] = true;
  pr[1] = true;
  for (long long i = 2; i <= sqrt(100005); i++) {
    for (long long j = i * 2; j <= sqrt(100005); j += i) {
      pr[j] = true;
    }
  }
}
vector<long long> divisor(long long n) {
  vector<long long> div;
  div.push_back(n);
  for (long long i = 2; i * i <= n; i++) {
    if (n % i == 0) {
      div.push_back(i);
      if (n / i != i) div.push_back(n / i);
    }
  }
  sort(div.begin(), div.end());
  return div;
}
long long modInverse(long long a, long long m) {
  long long m0 = m;
  long long y = 0, x = 1;
  if (m == 1) return 0;
  while (a > 1) {
    long long q = a / m;
    long long t = m;
    m = a % m, a = t;
    t = y;
    y = x - q * y;
    x = t;
  }
  if (x < 0) x += m0;
  return x;
}
long long find(long long n) {
  long long count = 0;
  while (n) {
    count++;
    n = n / 2;
  }
  return count;
}
void solve() {
  long long n;
  cin >> n;
  long long arr[n];
  for (long long i = 0; i < (long long)n; i++) cin >> arr[i];
  vector<vector<long long>> ans;
  if (n % 2 == 0) {
    long long ans1 = 0;
    for (long long i = 0; i < n; i++) {
      ans1 = ans1 ^ arr[i];
    }
    if (ans1 != 0) {
      cout << "NO\n";
      return;
    } else {
      cout << "YES\n";
      for (long long i = 0; i < n - 2; i += 2) {
        ans.push_back({i + 1, i + 2, i + 3});
      }
      for (long long i = 0; i < n - 2; i += 2) {
        ans.push_back({i + 1, i + 2, n});
      }
      ans.push_back({n - 2, n - 1, n});
      cout << ans.size() << "\n";
      for (long long i = 0; i < (long long)ans.size(); i++) {
        cout << ans[i][0] << " " << ans[i][1] << " " << ans[i][2] << "\n";
      }
      return;
    }
  }
  cout << "YES\n";
  for (long long i = 0; i < n - 2; i += 2) {
    ans.push_back({i + 1, i + 2, n});
    arr[n] = arr[n] ^ arr[i + 1] ^ arr[i + 2];
  }
  for (long long i = 0; i < n - 2; i += 2) {
    ans.push_back({i + 1, i + 2, n});
  }
  cout << ans.size() << "\n";
  for (long long i = 0; i < (long long)ans.size(); i++) {
    cout << ans[i][0] << " " << ans[i][1] << " " << ans[i][2] << "\n";
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  prim();
  for (long long i = 2; i <= 100005; i++) {
    if (pr[i] == false) {
      prime.push_back(i);
    }
  }
  long long t;
  t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
