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def gcd (a b : Nat) : Nat :=
  if b > 0 then gcd b (a % b) else a
termination_by b
decreasing_by
  rename_i h
  exact Nat.mod_lt a h

def N := 1000

def A := List.range N

def sum := (A.map fun x ↦ A.map (gcd x ·) |>.sum).sum

def sumParallel := (Task.mapList List.sum <| A.map fun x ↦ (Task.spawn fun _ ↦ A.map (gcd x ·) |>.sum)) |>.get

-- #eval sum
-- #eval sumParallel

def main := do
  IO.println "test"
  IO.println sum