code: private static FDBigInteger big5pow(int p) {
          assert p >= 0 : p; // negative power of 5
          if (p < MAX_FIVE_POW) {
              return POW_5_CACHE[p];
          }
          return big5powRec(p);
      }
docs: Computes <code>5</code> raised to a given power.
  
  @param p The exponent of 5.
  @return <code>5<sup>p</sup></code>.