modulo

type Calculator interface {
	N() int64                                        // N returns the positive integer that we're reducing by.
	MultiplyUint64(a uint64, b uint64) uint64        // MultiplyUint64 returns the product (a * b) mod N.
	MultiplyReducedUint64(a uint64, b uint64) uint64 // MultiplyReducedUint64 returns the product (a * b) mod N. Assumes that a and b are already reduced mod N (otherwise the result is undefined).
	MultiplyInt64(a int64, b int64) int64            // MultiplyInt64 returns the product (a * b) mod N.
	MultiplyReducedInt64(a int64, b int64) int64     // MultiplyReducedInt64 returns the product (a * b) mod N. Assumes that a and b are already reduced mod N (otherwise the result is undefined).
}