Move AOC into //scratch

Also rename it advent-of-code-2019 since I expect to participate this year as
well.

TODO: Should directories and files be name like-this or like_this?

scratch/advent-of-code-2019/day_1.py

@@ -0,0 +1,119 @@
+from math import floor
+
+xs = [
+    102473,
+    84495,
+    98490,
+    68860,
+    62204,
+    72810,
+    65185,
+    145951,
+    77892,
+    108861,
+    70764,
+    67286,
+    74002,
+    80773,
+    52442,
+    131505,
+    107162,
+    126993,
+    59784,
+    64231,
+    91564,
+    68585,
+    98735,
+    69020,
+    77332,
+    60445,
+    65826,
+    111506,
+    95431,
+    146687,
+    135119,
+    86804,
+    95915,
+    85434,
+    111303,
+    148127,
+    132921,
+    136213,
+    89004,
+    143137,
+    144853,
+    143017,
+    104386,
+    100612,
+    54760,
+    63813,
+    144191,
+    84481,
+    69718,
+    84936,
+    98621,
+    124993,
+    92736,
+    60369,
+    137284,
+    101902,
+    112726,
+    51784,
+    126496,
+    85005,
+    101661,
+    137278,
+    136637,
+    90340,
+    100209,
+    53683,
+    50222,
+    132060,
+    98797,
+    139054,
+    135638,
+    100632,
+    137849,
+    125333,
+    103981,
+    76954,
+    134352,
+    74229,
+    93402,
+    62552,
+    50286,
+    57066,
+    98439,
+    120708,
+    117827,
+    107884,
+    72837,
+    148663,
+    125645,
+    61460,
+    120555,
+    142473,
+    106668,
+    58612,
+    58576,
+    143366,
+    90058,
+    121087,
+    89546,
+    126161,
+]
+
+
+def fuel_for_mass(x):
+    """Return the amount of fuel (in mass) required for a mass of X. The total
+    amount of fuel includes the amount of fuel required for the fuel itself,
+    since fuel also has a mass weights."""
+    mass_fuel = floor(x / 3) - 2
+    if mass_fuel < 0:
+        return 0
+    else:
+        fuel_fuel = fuel_for_mass(mass_fuel)
+        return mass_fuel + fuel_fuel
+
+
+print(sum(fuel_for_mass(x) for x in xs))