diff --git a/2015/d25/ex1/ex1.py b/2015/d25/ex1/ex1.py
new file mode 100755
index 0000000..1b6cc03
--- /dev/null
+++ b/2015/d25/ex1/ex1.py
@@ -0,0 +1,43 @@
+#!/usr/bin/env python
+
+import sys
+from typing import NamedTuple
+
+
+class Point(NamedTuple):
+    x: int
+    y: int
+
+
+def solve(input: str) -> int:
+    def parse(input: str) -> tuple[int, int]:
+        *_, row, column = input.replace(".", "").split(", ")
+        return int(row.split()[-1]), int(column.split()[-1])
+
+    def mod_pow(n: int, pow: int, mod: int) -> int:
+        if pow == 0:
+            return 1
+        if pow == 1:
+            return n % mod
+        res = mod_pow(n, pow // 2, mod) ** 2
+        if pow % 2 == 1:
+            res *= n
+        return res % mod
+
+    def lookup(row: int, column: int) -> int:
+        n = column + row - 1
+        top_right = n * (n + 1) // 2
+        i = top_right - row
+        return 20151125 * mod_pow(252533, i, 33554393) % 33554393
+
+    row, column = parse(input)
+    return lookup(row, column)
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()