#include <bits/stdc++.h>
using namespace std;
int N;
int A[1 << 17];
int main() {
  scanf("%d", &N);
  int S = 0;
  for (int i = 0; i < N; i++) {
    scanf("%d", &A[i]);
    S ^= A[i];
  }
  if (N % 2 == 0 && S != 0) {
    puts("NO");
    return 0;
  }
  puts("YES");
  printf("%d\n", (N - 1) / 2 * 2 - 1);
  for (int i = 1; i + 1 < N; i += 2) printf("%d %d %d\n", 1, i + 1, i + 2);
  for (int i = 1; i + 3 < N; i += 2) printf("%d %d %d\n", 1, i + 1, i + 2);
}
