How to generate positive private key from negrative private key for bitcoin in bitcoinj java or kotlin

I used -13 as private key in bitcoin but the private key is not valid. How can I get the positive private key from -13 or any other negative numbers using Bitcoinj or java and generate the same address?

val params = MainNetParams.get()

val b = BigInteger("-13")
val key = ECKey.fromPrivate(b, false)
println(LegacyAddress.fromKey(params, key)) // 122Vo9PeKd4j8zSGBeQHdmks6GnkpycXNz

Answer

b.mod(new BigInteger("115792089237316195423570985008687907852837564279074904382605163141518161494337"))

Thanks to president-james-k-polk in the comments