http://idk.i2p/javadoc-i2p/net/i2p/crypto/eddsa/math/ed25519/Ed25519FieldElement.html
Preconditions: $|f|$ bounded by
$1.65*2^{26},1.65*2^{25},1.65*2^{26},1.65*2^{25},$ etc. $|g|$ bounded by
$1.65*2^{26},1.65*2^{25},1.65*2^{26},1.65*2^{25},$ etc. Postconditions: $|h|$ bounded by
$1.01*2^{25},1.01*2^{24},1.01*2^{25},1.01*2^{24},$ etc.