#include <bits/stdc++.h>
int x[100010];
int main() {
  int a;
  scanf("%d", &a);
  for (int i = 1; i <= a; i++) scanf("%d", &x[i]);
  if (a % 2 == 0) {
    int s = 0;
    for (int i = 1; i <= a; i++) s ^= x[i];
    if (s != 0) {
      printf("NO");
      return 0;
    }
    a--;
  }
  printf("YES\n");
  int count = 0;
  for (int i = 2; i <= a; i += 2) count += 2;
  printf("%d\n", count);
  for (int i = 2; i <= a; i += 2) printf("1 %d %d\n", i, i + 1);
  for (int i = 2; i <= a; i += 2) printf("1 %d %d\n", i, i + 1);
}
