diff --git a/src/day17.rs b/src/day17.rs
new file mode 100644
index 0000000..0a6aa30
--- /dev/null
+++ b/src/day17.rs
@@ -0,0 +1,108 @@
+use std::{fmt::Write, fs::read_to_string, io::BufRead, ops::BitXor};
+
+use itertools::Itertools;
+
+pub fn day_main() {
+    let input = read_to_string("input/day17.txt").unwrap();
+    let input = input.trim();
+    println!(" part1: {}", part1(input));
+    println!(" part2: {}", part2(input));
+}
+
+type RiddleResult = String;
+
+fn part1(input: &str) -> RiddleResult {
+    let (first, second) = input.split_once("\n\n").unwrap();
+    dbg!(first);
+    dbg!(second);
+    let mut registers = first.lines().map(|line| line.split_once(": ").unwrap().1);
+
+    let mut a = registers.next().unwrap().parse::<i64>().unwrap();
+    let mut b = registers.next().unwrap().parse::<i64>().unwrap();
+    let mut c = registers.next().unwrap().parse::<i64>().unwrap();
+
+    let program = second
+        .split_once(": ")
+        .unwrap()
+        .1
+        .split(",")
+        .map(|v| v.parse::<i64>().unwrap())
+        .collect_vec();
+
+    let mut ip = 0;
+    let mut output = String::new();
+
+    while ip < program.len() {
+        let opcode = program[ip];
+        let operand = program[(ip + 1) % program.len()];
+        // println!("a: {a}, b: {b}, c: {c}, op={opcode} {operand} (ip: {ip})");
+        match opcode {
+            0 => a = a / (2i64.pow(val(a, b, c, operand) as u32)),
+            1 => b = b.bitxor(operand),
+            2 => b = val(a, b, c, operand) % 8,
+            3 => {
+                if a == 0 {
+                } else {
+                    ip = operand as usize;
+                    continue;
+                }
+            }
+            4 => b = b.bitxor(c),
+            5 => output
+                .write_fmt(format_args!("{},", val(a, b, c, operand) % 8))
+                .unwrap(),
+            6 => b = a / (2i64.pow(val(a, b, c, operand) as u32)),
+            7 => c = a / (2i64.pow(val(a, b, c, operand) as u32)),
+            _ => panic!("illegal op code {}", opcode),
+        }
+        ip += 2;
+        // ip %= program.len();
+        // wait();
+    }
+    if output.ends_with(",") {
+        output.remove(output.len() - 1);
+    }
+    output
+}
+
+fn wait() {
+    let stdin = std::io::stdin();
+    let _line1 = stdin.lock().lines().next().unwrap().unwrap();
+}
+
+fn val(a: i64, b: i64, c: i64, operand: i64) -> i64 {
+    match operand {
+        0..=3 => operand,
+        4 => a,
+        5 => b,
+        6 => c,
+        _ => panic!("illegal operand {}", operand),
+    }
+}
+
+fn part2(_input: &str) -> RiddleResult {
+    String::new()
+}
+
+#[cfg(test)]
+mod test {
+    use super::{part1, part2};
+
+    const TEST_INPUT: &str = r"
+Register A: 729
+Register B: 0
+Register C: 0
+
+Program: 0,1,5,4,3,0
+    ";
+
+    #[test]
+    fn test1() {
+        assert_eq!(part1(TEST_INPUT.trim()), "4,6,3,5,6,3,5,2,1,0".to_string());
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(part2(TEST_INPUT.trim()), "".to_string());
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 9d8434a..3d6f108 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -14,5 +14,6 @@ pub mod day13;
 pub mod day14;
 pub mod day15;
 pub mod day16;
+pub mod day17;
 // PLACEHOLDER
 pub mod utils;
diff --git a/src/main.rs b/src/main.rs
index 4bb00b6..1d10e7c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -21,6 +21,7 @@ fn main() {
         (14, day14::day_main),
         (15, day15::day_main),
         (16, day16::day_main),
+        (17, day17::day_main),
         // PLACEHOLDER
     ]);
     let day: Option<u8> = args().nth(1).and_then(|a| a.parse().ok());