#include <bits/stdc++.h>
using namespace std;
const long long N = 300010;
long long n, x, t, T;
long long a[N];
int main() {
  scanf("%lld", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%lld", &a[i]);
    x = x ^ a[i];
  }
  if (n % 2 == 1) {
    puts("YES");
    printf("%d\n", n - 1);
    for (int i = 1; i < n; i += 2) {
      printf("%d %d %d\n", i, i + 1, i + 2);
    }
    for (int i = 1; i < n; i += 2) printf("%d %d %d\n", i, i + 1, n);
    return 0;
  }
  if (x != 0) {
    puts("NO");
    return 0;
  }
  puts("YES");
  n--;
  printf("%d\n", n - 1);
  for (int i = 1; i < n; i += 2) {
    printf("%d %d %d\n", i, i + 1, i + 2);
  }
  for (int i = 1; i < n; i += 2) printf("%d %d %d\n", i, i + 1, n);
  return 0;
}
