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diff --git a/15/main.py b/15/main.py
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+#!/usr/bin/python
+
+
+
+def parse_input(lines):
+    ingredients = []
+
+    for l in lines:
+        words = l.split()
+
+        # Rather than label the properties by name, we number them 0-4
+        props = []
+        for n in range(5):
+            props.append(int(words[2 + 2 * n].rstrip(",")))
+
+        name = words[0].rstrip(":")
+        ingredients.append(props)
+
+    return ingredients
+
+
+
+def all_recipes(ingredients):
+    recipes = {}
+
+    for i1 in range(101):
+        for i2 in range(101 - i1):
+            for i3 in range(101 - i1 - i2):
+                i4 = 100 - i1 - i2 - i3
+                amounts = [i1, i2, i3, i4] # amount of each ingredient
+
+                props = [0, 0, 0, 0] # score for each property
+                for p in range(len(props)):
+                    # Accumulate properties of ingredients
+                    for i in range(len(amounts)):
+                        prop = amounts[i] * ingredients[i][p]
+                        props[p] += prop
+                    # Clamp negative totals to zero
+                    if props[p] < 0:
+                        props[p] = 0
+
+                # `recipes' is a dictionary: key is recipe, value is total score
+                recipes[tuple(amounts)] = props[0] * props[1] * props[2] * props[3]
+
+    return recipes
+
+
+
+def solve_partn(partn, lines):
+    ingredients = parse_input(lines)
+    recipes = all_recipes(ingredients)
+
+    if partn == 2:
+        suitable = {}
+        for amounts, score in recipes.items():
+            calories = 0
+            for i in range(len(amounts)):
+                calories += amounts[i] * ingredients[i][4]
+            if calories == 500:
+                suitable[amounts] = score
+        recipes = suitable
+
+    return max(recipes.values())
+
+
+
+def main():
+    # Read ingredient information from input text file
+    with open("input.txt", "r") as f:
+        lines = f.read().splitlines()
+
+    print("Part 1 solution:", solve_partn(1, lines)) # 222870 for me
+    print("Part 2 solution:", solve_partn(2, lines)) # 117936 for me
+
+
+
+if __name__ == "__main__":
+    main()