diff --git a/src/day14.rs b/src/day14.rs
new file mode 100644
index 0000000..15163c2
--- /dev/null
+++ b/src/day14.rs
@@ -0,0 +1,149 @@
+use std::{collections::HashMap, iter::zip};
+
+use aoc_runner_derive::{aoc, aoc_generator};
+use itertools::{Itertools, iproduct};
+
+#[derive(Debug)]
+enum ProgramStep {
+    Mask(String),
+    Mem(u64, u64)
+}
+
+impl From<&str> for ProgramStep {
+    fn from(value: &str) -> Self {
+        let (name, value) = value.split(" = ").collect_tuple().unwrap();
+
+        return match name {
+            "mask" => Self::Mask(value.to_string()),
+            name if name.starts_with("mem") => {
+                Self::Mem(name[4..name.len() - 1].parse::<u64>().unwrap(), value.parse::<u64>().unwrap())
+            }
+            _ => unreachable!()
+        };
+    }
+}
+
+#[aoc_generator(day14)]
+fn parse(input: &str) -> Vec<ProgramStep> {
+    input.lines().map(ProgramStep::from).collect_vec()
+}
+
+fn apply_mask(mask: &str, val: u64) -> u64 {
+    let mut val = val;
+    for (i, char) in mask.chars().enumerate() {
+        match char {
+            'X' => continue,
+            '1' => val = val | (2_u64.pow((36 - i - 1).try_into().unwrap())),
+            '0' => val = val & !(2_u64.pow((36 - i - 1).try_into().unwrap())),
+            _ => unreachable!()
+        };
+    }
+
+    val
+}
+
+#[aoc(day14, part1)]
+fn part1(program: &Vec<ProgramStep>) -> u64 {
+    let mut mem: HashMap<u64, u64> = HashMap::new();
+    let mut mask = "";
+
+    for step in program {
+        match step {
+            ProgramStep::Mask(val) => mask = val,
+            ProgramStep::Mem(addr, val) => {
+                let val = apply_mask(mask, *val);
+                mem.insert(*addr, val);
+            },
+        }
+    }
+    mem.values().sum()
+}
+
+fn permute_masks(mask: &str) -> Vec<String> {
+    let mut masks: Vec<String> = vec![];
+    let bits = mask.chars().enumerate().filter(|(_, v)| *v == 'X').map(|(i, _)| i).collect_vec();
+    let perms = kproduct("21".to_string(), bits.len() as u32);
+
+    let mut new_mask = mask.to_string();
+    for perm in perms {
+        let bit_vals = zip(bits.clone(), perm.chars()).collect::<HashMap<usize, char>>();
+        for (k, val) in bit_vals {
+            new_mask = new_mask[0..k].to_string() + &val.to_string() + &new_mask[k+1..];
+        }
+        masks.push(new_mask.clone());
+    }
+    masks
+}
+
+fn kproduct(seq: String, k: u32) -> Vec<String> {
+    match k {
+        0 => vec![],
+        1 => seq.chars().map(|c| c.to_string()).collect(),
+        2 => iproduct!(seq.chars(), seq.chars()).map(|(a, b)| format!("{}{}", a, b)).collect(),
+        _ => iproduct!(kproduct(seq.clone(), k - 1), seq.chars()).map(|(a, b)| format!("{}{}", a, b)).collect(),
+    }
+}
+
+fn get_addrs(addr: u64, mask: &str) -> Vec<u64> {
+    let mut addrs = vec![];
+    let masks = permute_masks(mask);
+    for mask in masks {
+        let mut addr = addr;
+        for (i, char) in mask.chars().enumerate() {
+            match char {
+                '1' => addr = addr | (2_u64.pow((36 - i - 1).try_into().unwrap())),
+                '2' => addr = addr & !(2_u64.pow((36 - i - 1).try_into().unwrap())),
+                '0' => continue,
+                _ => unreachable!()
+            }
+        }
+        addrs.push(addr)
+    }
+    addrs
+}
+
+#[aoc(day14, part2)]
+fn part2(program: &Vec<ProgramStep>) -> u64 {
+    let mut mem: HashMap<u64, u64> = HashMap::new();
+    let mut mask = "";
+
+    for step in program {
+        match step {
+            ProgramStep::Mask(val) => mask = val,
+            ProgramStep::Mem(addr, val) => {
+                let addrs = get_addrs(*addr, mask);
+                for addr in addrs {
+                    mem.insert(addr, *val);
+                }
+            },
+        }
+    }
+
+    mem.values().sum()
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+const EX: &str = r"mask = XXXXXXXXXXXXXXXXXXXXXXXXXXXXX1XXXX0X
+mem[8] = 11
+mem[7] = 101
+mem[8] = 0";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&parse(EX)), 165);
+    }
+
+const EX_2: &str = r"mask = 000000000000000000000000000000X1001X
+mem[42] = 100
+mask = 00000000000000000000000000000000X0XX
+mem[26] = 1";
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&parse(EX_2)), 208);
+    }
+}
\ No newline at end of file
diff --git a/src/day9.rs b/src/day9.rs
index e6d5e81..66a1bb2 100644
--- a/src/day9.rs
+++ b/src/day9.rs
@@ -1,7 +1,7 @@
 use aoc_runner_derive::{aoc, aoc_generator};
 use itertools::Itertools;
 
-const PREAMBLE_LEN: usize = 25;
+const PREAMBLE_LEN: usize = 5;
 
 #[aoc_generator(day9)]
 fn parse(input: &str) -> Vec<u64> {
diff --git a/src/lib.rs b/src/lib.rs
index c08e87f..695ff83 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,4 @@
+mod day14;
 mod day13;
 mod day12;
 mod day10;