#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class t, class u>
void chmax(t& first, u second) {
  if (first < second) first = second;
}
template <class t, class u>
void chmin(t& first, u second) {
  if (second < first) first = second;
}
template <class t>
using vc = vector<t>;
template <class t>
using vvc = vc<vc<t>>;
using pi = pair<ll, ll>;
using vi = vc<ll>;
template <class t, class u>
ostream& operator<<(ostream& os, const pair<t, u>& p) {
  return os << "{" << p.first << "," << p.second << "}";
}
template <class t>
ostream& operator<<(ostream& os, const vc<t>& v) {
  os << "{";
  for (auto e : v) os << e << ",";
  return os << "}";
}
using uint = unsigned;
using ull = unsigned long long;
template <ll i, class T>
void print_tuple(ostream&, const T&) {}
template <ll i, class T, class H, class... Args>
void print_tuple(ostream& os, const T& t) {
  if (i) os << ",";
  os << get<i>(t);
  print_tuple<i + 1, T, Args...>(os, t);
}
template <class... Args>
ostream& operator<<(ostream& os, const tuple<Args...>& t) {
  os << "{";
  print_tuple<0, tuple<Args...>, Args...>(os, t);
  return os << "}";
}
void print(ll x, ll suc = 1) {
  cout << x;
  if (suc == 1) cout << endl;
  if (suc == 2) cout << " ";
}
ll read() {
  ll i;
  cin >> i;
  return i;
}
vi readvi(ll n, ll off = 0) {
  vi v(n);
  for (ll i = ll(0); i < ll(n); i++) v[i] = read() + off;
  return v;
}
template <class T>
void print(const vector<T>& v, ll suc = 1) {
  for (ll i = ll(0); i < ll(v.size()); i++)
    print(v[i], i == ll(v.size()) - 1 ? suc : 2);
}
string readString() {
  string s;
  cin >> s;
  return s;
}
template <class T>
T sq(const T& t) {
  return t * t;
}
void yes(bool ex = true) {
  cout << "Yes" << endl;
  if (ex) exit(0);
}
void no(bool ex = true) {
  cout << "No" << endl;
  if (ex) exit(0);
}
constexpr ll ten(ll n) { return n == 0 ? 1 : ten(n - 1) * 10; }
const ll infLL = LLONG_MAX / 3;
const ll inf = infLL;
ll topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }
ll topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }
ll popcount(signed t) { return __builtin_popcount(t); }
ll popcount(ll t) { return __builtin_popcountll(t); }
bool ispow2(ll i) { return i && (i & -i) == i; }
bool inc(ll first, ll second, ll c) { return first <= second && second <= c; }
template <class t>
void mkuni(vc<t>& v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
}
ll rand_int(ll l, ll r) {
  static random_device rd;
  static mt19937 gen(rd());
  return uniform_int_distribution<ll>(l, r)(gen);
}
signed main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
  vc<tuple<ll, ll, ll>> ans;
  auto brute = [&](ll cur, ll m, ll o) {
    vi w;
    for (ll i = ll(0); i < ll(m); i++)
      for (ll j = ll(i + 1); j < ll(m); j++) {
        ll k = j * 2 - i;
        if (k < m) w.push_back((1 << i) + (1 << j) + (1 << k));
      }
    ll s = w.size();
    ll res = -1;
    for (ll bit = ll(0); bit < ll(1 << s); bit++) {
      ll x = cur;
      for (ll i = ll(0); i < ll(s); i++)
        if (bit & 1 << i) x ^= w[i];
      if (x == 0 && popcount(res) > popcount(bit)) res = bit;
    }
    if (res == -1) {
      no();
    }
    for (ll i = ll(0); i < ll(s); i++)
      if (res & 1 << i) {
        ll z[3];
        for (ll k = ll(0); k < ll(3); k++) {
          z[k] = topbit(w[i]);
          w[i] ^= 1 << z[k];
        }
        reverse(z, z + 3);
        ans.emplace_back(o + z[0], o + z[1], o + z[2]);
      }
  };
  ll n;
  cin >> n;
  vi first = readvi(n);
  auto flip = [&](ll x, ll y, ll z) {
    first[x] ^= 1;
    first[y] ^= 1;
    first[z] ^= 1;
    ans.emplace_back(x, y, z);
  };
  deque<ll> idx;
  for (ll i = ll(0); i < ll(n); i++) idx.push_back(i);
  while (idx.size() > 8) {
    while (idx.size() > 8) {
      ll i = idx[0];
      if (first[i] == 0) {
        idx.pop_front();
        continue;
      }
      if (first[i + 1] == 0) {
        if (first[i + 2] == 0) {
          flip(i, i + 3, i + 6);
        } else {
          flip(i, i + 2, i + 4);
        }
      } else {
        if (first[i + 2] == 0) {
          break;
        } else {
          flip(i, i + 1, i + 2);
        }
      }
    }
    while (idx.size() > 8) {
      ll i = idx.back();
      if (first[i] == 0) {
        idx.pop_back();
        continue;
      }
      if (first[i - 1] == 0) {
        if (first[i - 2] == 0) {
          flip(i - 6, i - 3, i);
        } else {
          flip(i - 4, i - 2, i);
        }
      } else {
        if (first[i - 2] == 0) {
          break;
        } else {
          flip(i - 2, i - 1, i);
        }
      }
    }
    if (idx.size() > 8) {
      ll i = idx.front(), j = idx.back();
      if ((i + j) % 2 == 0) {
        flip(i, (i + j) / 2, j);
        flip(i + 1, (i + j) / 2, j - 1);
      } else {
        flip(i, (i + j - 1) / 2, j - 1);
        flip(i + 1, (i + 1 + j) / 2, j);
      }
    }
  }
  ll cur = 0, m = idx.size();
  for (ll i = ll(0); i < ll(m); i++) cur += first[idx[i]] << i;
  brute(cur, m, idx.front());
  yes(0);
  cout << ans.size() << endl;
  for (auto v : ans) {
    ll x, y, z;
    tie(x, y, z) = v;
    cout << x + 1 << " " << y + 1 << " " << z + 1 << "\n";
  }
}
