#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  int n;
  cin >> n;
  int xr = 0;
  pair<int, int> a[n];
  for (int i = 0; i < n; i++)
    cin >> a[i].first, a[i].second = i, xr ^= a[i].first;
  if (n % 2 == 0 && xr != 0) {
    cout << "NO" << '\n';
    return 0;
  }
  sort(a, a + n);
  vector<tuple<int, int, int>> ans;
  for (int i = 1; i < n - 1; i += 2) {
    ans.push_back({a[i].second + 1, a[i - 1].second + 1, a[n - 1].second + 1});
  }
  for (int i = 1; i < n - 1; i += 2) {
    ans.push_back({a[i].second + 1, a[i - 1].second + 1, a[n - 1].second + 1});
  }
  cout << "YES" << '\n';
  cout << ans.size() << '\n';
  for (int i = 0; i < ans.size(); i++) {
    cout << get<0>(ans[i]) << " " << get<1>(ans[i]) << " " << get<2>(ans[i])
         << '\n';
  }
  return 0;
}
