#include <bits/stdc++.h>
using namespace std;
template <class A>
void pr(A a) {
  cout << a;
  cout << '\n';
}
template <class A, class B>
void pr(A a, B b) {
  cout << a << ' ';
  pr(b);
}
template <class A, class B, class C>
void pr(A a, B b, C c) {
  cout << a << ' ';
  pr(b, c);
}
template <class A, class B, class C, class D>
void pr(A a, B b, C c, D d) {
  cout << a << ' ';
  pr(b, c, d);
}
template <class A>
void PR(A a, long long n) {
  for (long long i = (long long)(0); i < (long long)(n); i++) {
    if (i) cout << ' ';
    cout << a[i];
  }
  cout << '\n';
}
long long check(long long n, long long m, long long x, long long y) {
  return x >= 0 && x < n && y >= 0 && y < m;
}
const long long MAX = 1e9 + 7, MAXL = 1LL << 61, dx[4] = {-1, 0, 1, 0},
                dy[4] = {0, 1, 0, -1};
int d[1 << 15], p[1 << 15];
pair<int, pair<int, int> > q[1 << 15];
void Main() {
  long long n;
  cin >> n;
  queue<int> que;
  que.push(0);
  memset(p, -1, sizeof(p));
  d[0] = 1;
  long long m = min(n, 15LL);
  while (!que.empty()) {
    int x = que.front();
    que.pop();
    for (long long i = (long long)(0); i < (long long)(m); i++)
      for (long long j = (long long)(i + 1); j < (long long)(m); j++) {
        int k = j + abs(i - j);
        if (k >= m) continue;
        int t = x;
        t ^= 1 << i;
        t ^= 1 << j;
        t ^= 1 << k;
        if (!d[t]) {
          d[t] = 1;
          p[t] = x;
          q[t] = pair<int, pair<int, int> >(i, pair<int, int>(j, k));
          que.push(t);
        }
      }
  }
  vector<pair<int, pair<int, int> > > ans;
  long long a[n];
  for (long long i = (long long)(0); i < (long long)(n); i++) cin >> a[i];
  if (n >= 15) {
    for (long long i = (long long)(n)-1; i >= 0; i--) {
      if (i < 15) break;
      if (a[i]) {
        int f = 0;
        for (long long j = (long long)(i - 1) - 1; j >= 0; j--) {
          if (a[j]) {
            int k = j - abs(i - j);
            if (k >= 0) {
              ans.push_back(
                  pair<int, pair<int, int> >(k, pair<int, int>(j, i)));
              a[i] ^= 1;
              a[j] ^= 1;
              a[k] ^= 1;
            } else if (abs(i - j) % 2 == 0) {
              int k = (i + j) / 2;
              ans.push_back(
                  pair<int, pair<int, int> >(j, pair<int, int>(k, i)));
              a[i] ^= 1;
              a[j] ^= 1;
              a[k] ^= 1;
            } else {
              j = 0;
              if (abs(i - j) % 2) j = 1;
              int k = (i + j) / 2;
              ans.push_back(
                  pair<int, pair<int, int> >(j, pair<int, int>(k, i)));
              a[i] ^= 1;
              a[j] ^= 1;
              a[k] ^= 1;
            }
            f = 1;
            break;
          }
        }
        if (!f) {
          int j = 0;
          if (abs(i - j) % 2) j = 1;
          int k = (i + j) / 2;
          ans.push_back(pair<int, pair<int, int> >(j, pair<int, int>(k, i)));
          a[i] ^= 1;
          a[j] ^= 1;
          a[k] ^= 1;
        }
      }
    }
  }
  int t = 0;
  for (long long i = (long long)(0); i < (long long)(m); i++) {
    if (a[i]) t |= 1 << i;
  }
  if (!d[t]) {
    pr("NO");
    return;
  }
  while (t) {
    ans.push_back(q[t]);
    t = p[t];
  }
  pr("YES");
  pr(ans.size());
  for (long long i = (long long)(0); i < (long long)(ans.size()); i++)
    pr(ans[i].first + 1, ans[i].second.first + 1, ans[i].second.second + 1);
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  Main();
  return 0;
}
