From 0a441ce2306ae9edefb009fbc0596f4d511cdc7f Mon Sep 17 00:00:00 2001
From: blenovo <bk@gmail.com>
Date: Wed, 6 Aug 2025 00:51:06 +0200
Subject: summertime warmup session - finish

---
 2020/aoc2020-d25.py | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 2020/aoc2020-d25.py

(limited to '2020/aoc2020-d25.py')

diff --git a/2020/aoc2020-d25.py b/2020/aoc2020-d25.py
new file mode 100644
index 0000000..28d1afe
--- /dev/null
+++ b/2020/aoc2020-d25.py
@@ -0,0 +1,29 @@
+#advent of code 2020
+#day 25
+#I made a mistake by thinking that subject number is an unknow
+#while in reality it actually is =7 as in puzzle description
+
+def FindNumbers(pubkey):
+	S = 7;
+	L = 0;
+	v = 1;
+	while True:
+		L += 1;
+		v *= S;
+		v = v%20201227;
+		if v == pubkey:
+			return L; #gives loop number
+
+PuzzleInput = open("25.in","r").read().split("\n");
+cardkey = int(PuzzleInput[0]);
+doorkey = int(PuzzleInput[1]);
+#encryption key is the same 
+#whether we use loop of card + subject of door
+#or loop of door + subject of card
+encryption = 1;
+for l in range(FindNumbers(cardkey)):
+	encryption *= doorkey;
+	encryption = encryption%20201227;
+
+part1 = encryption; 
+print("part 1 =", part1);
-- 
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