#include <bits/stdc++.h>
using namespace std;
long long a[(100010)];
signed main() {
  long long n, xors = 0;
  cin >> n;
  for (long long i = 1; i <= n; i++) {
    scanf("%lld", &a[i]);
    xors ^= a[i];
  }
  if (n % 2) {
    printf("YES\n");
    printf("%lld\n", n - 1);
    for (long long i = 1; i + 1 <= n; i += 2) {
      printf("%lld %lld %lld\n", i, i + 1, i + 2);
    }
    for (long long i = 1; i + 1 <= n; i += 2) {
      printf("%lld %lld %lld\n", i, i + 1, n);
    }
  } else {
    if (xors) {
      printf("NO\n");
      return 0;
    }
    printf("YES\n");
    printf("%lld\n", n - 2);
    for (long long i = 1; i + 2 <= n; i += 2) {
      printf("%lld %lld %lld\n", i, i + 1, i + 2);
    }
    for (long long i = 1; i + 2 <= n; i += 2) {
      printf("%lld %lld %lld\n", i, i + 1, n);
    }
  }
  return 0;
}
