#include <bits/stdc++.h>
using namespace std;
const long long mod = 998244353;
const int N = 1e5 + 5;
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }
template <typename T, typename V>
void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T>
void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x) cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cerr << ", ";
  _print(v...);
}
vector<vector<int> > ans;
void solve(int n) {
  int i = 1, j = 2, k = 3;
  while (k <= n) {
    ans.push_back({i, j, k});
    i += 2;
    j += 2;
    k += 2;
  }
  i = 1, j = 2, k -= 2;
  while (j < n - 1) {
    ans.push_back({i, j, k});
    i += 2, j += 2;
  }
}
void solve() {
  int n;
  cin >> n;
  long long a[n];
  long long x = 0;
  for (long long i = 0; i < n; i++) {
    cin >> a[i];
    x ^= a[i];
  }
  if (n % 2 == 0) {
    if (x) {
      cout << "NO\n";
      return;
    } else {
      solve(n - 1);
    }
  } else {
    solve(n);
  }
  cout << "YES\n";
  cout << ans.size() << '\n';
  for (auto v : ans) {
    printf("%d %d %d\n", v[0], v[1], v[2]);
  }
}
signed main() {
  int t = 1;
  for (long long i = 1; i < t + 1; i++) {
    solve();
  }
  return 0;
}
