diff --git a/README.md b/README.md
index 1e757bbe..9b97068e 100644
--- a/README.md
+++ b/README.md
@@ -20,10 +20,11 @@ See the [examples](./examples/) and [tests](./tests/) directories for more examp
 or read [the Jou tutorial](./doc/tutorial.md).
 
 For now, Jou is great for writing small programs that don't have a lot of dependencies.
-For example, I solved all problems of [Advent of Code 2023](https://adventofcode.com/2023/) in Jou,
-and I'm currently working on Advent of Code 2024.
-See [examples/aoc2023](./examples/aoc2023/)
-and [examples/aoc2024](./examples/aoc2024/) for the code.
+For example, I solved all problems of
+[Advent of Code 2023](https://adventofcode.com/2023/) and
+[Advent of Code 2024](https://adventofcode.com/2024/) with Jou. See
+[examples/aoc2023](./examples/aoc2023/) and
+[examples/aoc2024](./examples/aoc2024/) for the code.
 
 I think Jou will be useful for two kinds of people:
 - People who find C programming fun but like Python's syntax
diff --git a/examples/aoc2024/day25/part1.jou b/examples/aoc2024/day25/part1.jou
new file mode 100644
index 00000000..3ffd4cda
--- /dev/null
+++ b/examples/aoc2024/day25/part1.jou
@@ -0,0 +1,56 @@
+import "stdlib/io.jou"
+import "stdlib/mem.jou"
+import "../../aoc2023/grid.jou"
+
+
+def fits(key: int*, lock: int*) -> bool:
+    for i = 0; i < 5; i++:
+        if key[i] + lock[i] > 5:
+            return False
+    return True
+
+
+def main() -> int:
+    f = fopen("sampleinput.txt", "r")
+    assert f != NULL
+
+    keys: int[5][500]
+    locks: int[5][500]
+    nkeys = 0
+    nlocks = 0
+
+    while feof(f) == 0:
+        grid = read_grid_from_file(f)
+        assert grid.width == 5
+        assert grid.height == 7
+
+        dest: int*
+        if grid.get([0, 0]) == '#':
+            # lock
+            assert nlocks < sizeof(locks)/sizeof(locks[0])
+            dest = locks[nlocks++]
+        else:
+            # key
+            assert nkeys < sizeof(keys)/sizeof(keys[0])
+            dest = keys[nkeys++]
+
+        for x = 0; x < 5; x++:
+            count = -1  # ignore one full row
+            for y = 0; y < 7; y++:
+                if grid.get([x, y]) == '#':
+                    count++
+            assert count >= 0
+            dest[x] = count
+
+        free(grid.data)
+
+    fclose(f)
+
+    result = 0
+    for il = 0; il < nlocks; il++:
+        for ik = 0; ik < nkeys; ik++:
+            if fits(keys[ik], locks[il]):
+                result++
+
+    printf("%d\n", result)  # Output: 3
+    return 0
diff --git a/examples/aoc2024/day25/sampleinput.txt b/examples/aoc2024/day25/sampleinput.txt
new file mode 100644
index 00000000..8e298551
--- /dev/null
+++ b/examples/aoc2024/day25/sampleinput.txt
@@ -0,0 +1,39 @@
+#####
+.####
+.####
+.####
+.#.#.
+.#...
+.....
+
+#####
+##.##
+.#.##
+...##
+...#.
+...#.
+.....
+
+.....
+#....
+#....
+#...#
+#.#.#
+#.###
+#####
+
+.....
+.....
+#.#..
+###..
+###.#
+###.#
+#####
+
+.....
+.....
+.....
+#....
+#.#..
+#.#.#
+#####