#include <bits/stdc++.h>
using namespace std;
const long long INF = 9223372036854775807;
const long long MOD = 1000000007;
const long double PI = acos(-1);
inline long long power(long long a, long long b, long long z = MOD) {
  long long res = 1;
  a = (a % z);
  while (b) {
    if (b & 1) res = (res * a) % z;
    a = (a * a) % z;
    b = b >> 1;
  }
  return res;
}
inline long long inverse(long long a, long long z = MOD) {
  return power(a, z - 2, z);
}
long long extend(long long a, long long b, long long &x, long long &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  long long x1, y1;
  long long g = extend(b, a % b, x1, y1);
  x = y1;
  y = x1 - (a / b) * y1;
  return g;
}
inline long long mat_power(long long a, long long b, long long c, long long d,
                           long long n, long long z = MOD) {
  long long a0 = 1, b0 = 0, c0 = 0, d0 = 1;
  while (n) {
    if (n & 1) {
      long long a1 = a0, b1 = b0, c1 = c0, d1 = d0;
      a0 = (a1 * a + b1 * c) % z;
      b0 = (a1 * b + b1 * d) % z;
      c0 = (c1 * a + d1 * c) % z;
      d0 = (c1 * b + d1 * d) % z;
    }
    long long a1 = a, b1 = b, c1 = c, d1 = d;
    a = (a1 * a1 + b1 * c1) % z;
    b = (a1 * b1 + b1 * d1) % z;
    c = (c1 * a1 + d1 * c1) % z;
    d = (c1 * b1 + d1 * d1) % z;
    n = n >> 1;
  }
  return c0;
}
void odd(int aray[], int n) {
  vector<pair<int, pair<int, int> > > ans;
  for (int i = 1; i + 2 <= n; i += 2)
    ans.push_back(make_pair(i, make_pair(i + 1, i + 2)));
  for (int i = 1; i <= n - 4; i += 2)
    ans.push_back(make_pair(i, make_pair(i + 1, n)));
  cout << "YES\n";
  cout << ans.size() << "\n";
  for (auto x : ans)
    cout << x.first << " " << x.second.first << " " << x.second.second << "\n";
  return;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;
  int aray[n];
  for (int i = 0; i < n; i++) cin >> aray[i];
  if (n & 1)
    odd(aray, n);
  else {
    long long sum = 0;
    for (int i = 0; i < n; i++) sum = sum ^ aray[i];
    if (sum == 0)
      odd(aray, n - 1);
    else
      cout << "NO\n";
  }
  return 0;
}
