diff --git a/2021/d05/ex1/ex1.py b/2021/d05/ex1/ex1.py
new file mode 100755
index 0000000..2031251
--- /dev/null
+++ b/2021/d05/ex1/ex1.py
@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+
+import itertools
+import sys
+from collections import Counter
+from typing import Iterable, List, NamedTuple, Tuple
+
+
+class Point(NamedTuple):
+    x: int
+    y: int
+
+
+Line = Tuple[Point, Point]
+
+
+def solve(input: List[str]) -> int:
+    def parse_line(line: str) -> Line:
+        def parse_point(point: str) -> Point:
+            x, y = map(int, point.split(","))
+            return Point(x, y)
+
+        p1, p2 = map(parse_point, line.split(" -> "))
+        return (p1, p2)
+
+    def is_of_interest(line: Line) -> bool:
+        p1, p2 = line
+        return p1.x == p2.x or p1.y == p2.y
+
+    def line_to_points(line: Line) -> Iterable[Point]:
+        def inclusive_range_any_order(a: int, b: int) -> Iterable[int]:
+            if a < b:
+                yield from range(a, b + 1)
+            else:
+                yield from range(a, b - 1, -1)
+
+        p1, p2 = line
+
+        if p1.x == p2.x:
+            for y in inclusive_range_any_order(p1.y, p2.y):
+                yield Point(p1.x, y)
+            return
+
+        if p1.y == p2.y:
+            for x in inclusive_range_any_order(p1.x, p2.x):
+                yield Point(x, p1.y)
+            return
+
+        assert False  # Sanity check
+
+    lines = list(filter(is_of_interest, map(parse_line, input)))
+    counts = Counter(itertools.chain.from_iterable(line_to_points(l) for l in lines))
+
+    return sum(counts[p] > 1 for p in counts)
+
+
+def main() -> None:
+    input = [line.strip() for line in sys.stdin.readlines()]
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()