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def call(axn, axd, ayn, ayd):
if !axn and !ayn:
return([0, 1, 0, 1], 4)
with P = -4294968273:
# No need to add (A, 1) because A = 0 for bitcoin
with mn = mulmod(mulmod(mulmod(axn, axn, P), 3, P), ayd, P):
with md = mulmod(mulmod(axd, axd, P), mulmod(ayn, 2, P), P):
with msqn = mulmod(mn, mn, P):
with msqd = mulmod(md, md, P):
with xn = addmod(mulmod(msqn, axd, P), P - mulmod(msqd, mulmod(axn, 2, P), P), P):
with xd = mulmod(msqd, axd, P):
with mamxn = mulmod(addmod(mulmod(axn, xd, P), P - mulmod(axd, xn, P), P), mn, P):
with mamxd = mulmod(mulmod(axd, xd, P), md, P):
with yn = addmod(mulmod(mamxn, ayd, P), P - mulmod(mamxd, ayn, P), P):
with yd = mulmod(mamxd, ayd, P):
return([xn, xd, yn, yd], 4)
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