Returns a BigInteger whose value is {@code (this}<sup>-1</sup> {@code mod m)}.
@param m the modulus.
@return {@code this}<sup>-1</sup> {@code mod m}.
@throws ArithmeticException {@code m} ≤ 0, or this BigInteger
has no multiplicative inverse mod m (that is, this BigInteger
is not <i>relatively prime</i> to m).
Returns a BigInteger whose value is {@code (this}<sup>-1</sup> {@code mod m)}.
@param m the modulus. @return {@code this}<sup>-1</sup> {@code mod m}. @throws ArithmeticException {@code m} ≤ 0, or this BigInteger has no multiplicative inverse mod m (that is, this BigInteger is not <i>relatively prime</i> to m).