Constant curve25519_dalek::constants::MSQRT_M1

pub const MSQRT_M1: FieldElement = FieldElement([32595792, 7943725, -9377950, -3500415, -12389472, 272473,
              25146209, 2005654, -326686, -11406482])

Precomputed value of the other square root of -1 (mod p), i.e., MSQRT_M1 = -SQRT_M1.