#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  vector<int> a(n);
  set<int> s;
  int g = 0;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    g ^= a[i];
    s.insert(a[i]);
  }
  if (n == 3) {
    printf("YES\n");
    printf("1\n");
    printf("1 2 3\n");
    return 0;
  }
  if (n % 2 == 0 and g > 0) {
    printf("NO\n");
    return 0;
  }
  if (n % 2 == 0) {
    printf("YES\n");
    vector<pair<int, pair<int, int>>> v;
    for (int i = 1;; i += 2) {
      if (i + 2 > n) break;
      v.push_back(make_pair(i, make_pair(i + 1, i + 2)));
    }
    for (int i = 1;; i += 2) {
      if (i + 3 == n) break;
      v.push_back(make_pair(i, make_pair(i + 1, n)));
    }
    printf("%d\n", v.size());
    for (auto p : v) {
      printf("%d %d %d\n", p.first, p.second.first, p.second.second);
    }
    return 0;
  } else {
    printf("YES\n");
    vector<pair<int, pair<int, int>>> v;
    for (int i = 1;; i += 2) {
      if (i + 2 > n) break;
      v.push_back(make_pair(i, make_pair(i + 1, i + 2)));
    }
    for (int i = 1;; i += 2) {
      if (i + 2 == n) break;
      v.push_back(make_pair(i, make_pair(i + 1, n)));
    }
    printf("%d\n", v.size());
    for (auto p : v) {
      printf("%d %d %d\n", p.first, p.second.first, p.second.second);
    }
    return 0;
  }
}
