diff --git a/2021/d24.py b/2021/d24.py
index 773a700..08c5cba 100644
--- a/2021/d24.py
+++ b/2021/d24.py
@@ -2,62 +2,44 @@ from lib import get_data
 
 data = get_data(__file__)
 
-# lines = data.splitlines()
-# blocks = [lines[i:i + 18] for i in range(0, len(lines), 18)]
-# blocks = zip(*blocks)
-# for row in blocks:
-#     print("; ".join(set(row)))
 
-def run(number=None):
-    inputs = []
-    if number is not None:
-        for c in str(number):
-            if c == "0":
-                return
-            inputs.append(int(c))
-        inputs = list(reversed(inputs))
-    else:
-        inputs = None
+def run(number):
+    inputs = list(map(int, str(number)))
+    assert len(inputs) == 14
 
-    regs = {c: 0 for c in "wxyz"}
-    for i, line in enumerate(data.splitlines()):
-        if line.startswith("inp"):
-            if inputs is not None:
-                if inputs == []:
-                    print(number, regs)
-                    return
-                else:
-                    op, a = line.split()
-                    regs[a] = inputs.pop()
-            else:
-                # print(regs)
-                op, a = line.split()
-                regs[a] = int(input(f"{i // 14} > "))
-            continue
+    w, x, z = 0, 0, 0
+    i = 0
+    for i in range(len(inputs)):
+        w = inputs[i]
+        # print(f"{w=:3} {x=:3}                       {z=}")
 
-        op, a, b = line.split()
-        b = regs[b] if b in regs else int(b)
-        match op:
-            case "add":
-                regs[a] = regs[a] + b
-            case "mul":
-                regs[a] = regs[a] * b
-            case "div":
-                regs[a] = regs[a] // b
-            case "mod":
-                regs[a] = regs[a] % b
-            case "eql":
-                regs[a] = 1 if regs[a] == b else 0
+        to_add_x = [15, 15, 12, 13, -12, 10, -9, 14, 13, -14, -11, -2, -16, -14][i]
+        to_div_z = [1, 1, 1, 1, 26, 1, 26, 1, 1, 26, 26, 26, 26, 26][i]
+        to_add_z = [15, 10, 2, 16, 12, 11, 5, 16, 6, 15, 3, 12, 10, 13][i]
+
+        zz = z
+        x = (z % 26) + to_add_x
+        z = z // to_div_z
+
+        # print(f"{zz % 26=} + {to_add_x=} {x=}")
+
+        if x == w:
+            # print(f"added                     = 0")
+            pass
+        else:
+            z *= 26
+            z += w + to_add_z
+            # print(f"added {w=} + {to_add_z=} = {w + to_add_z}")
+        # print()
+
+    # print(f"\nEND:\n{w=} {x=} {z=}", "\n" * 15)
+    return z
 
 
-    print("end", inputs, number, regs)
+largest_model_nr = 89959794919939
+assert run(largest_model_nr) == 0
+print(largest_model_nr)
 
-
-run(19111111111111)
-
-# while True:
-#     try:
-#         run()
-#     except KeyboardInterrupt:
-#         print("\n restart <")
-#         pass
+lowest_model_nr = 17115131916112
+assert run(lowest_model_nr) == 0
+print(lowest_model_nr)
diff --git a/README.md b/README.md
index 73e890b..da35e5e 100644
--- a/README.md
+++ b/README.md
@@ -195,7 +195,7 @@ Solutions and utility script for Advent of Code challenges in Python.
 - Day 21:  37:45   (Wasn't hard but I was just too slow.)
 - Day 22:
 - Day 23:  81:38   (Fun but obviously not competitive.)
-- Day 24:
+- Day 24: 232:00   (Super hard for me but I am proud of it.)
 - Day 25:  15:43   (That could have been much much faster.)
 
 ## AoC 2022