#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5;
int a[MAXN];
int main(void) {
  int n;
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
  int sum = 0;
  for (int i = 1; i <= n; ++i) sum ^= a[i];
  if (n % 2 == 0 && sum) return printf("NO"), 0;
  printf("YES\n%d\n", (n - 1) / 2 * 2);
  for (int i = 2; i + 1 <= n; i += 2) printf("%d %d %d\n", 1, i, i + 1);
  for (int i = 2; i + 1 <= n; i += 2) printf("%d %d %d\n", 1, i, i + 1);
  return 0;
}
