diff --git a/3/Cargo.lock b/3/Cargo.lock
new file mode 100644
index 0000000..4c00902
--- /dev/null
+++ b/3/Cargo.lock
@@ -0,0 +1,54 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "aho-corasick"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e60d3430d3a69478ad0993f19238d2df97c507009a52b3c10addcd7f6bcb916"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "day3"
+version = "0.1.0"
+dependencies = [
+ "regex",
+]
+
+[[package]]
+name = "memchr"
+version = "2.7.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
+
+[[package]]
+name = "regex"
+version = "1.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b544ef1b4eac5dc2db33ea63606ae9ffcfac26c1416a2806ae0bf5f56b201191"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-automata"
+version = "0.4.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "809e8dc61f6de73b46c85f4c96486310fe304c434cfa43669d7b40f711150908"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2b15c43186be67a4fd63bee50d0303afffcef381492ebe2c5d87f324e1b8815c"
diff --git a/3/Cargo.toml b/3/Cargo.toml
new file mode 100644
index 0000000..0275d9d
--- /dev/null
+++ b/3/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "day3"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+regex = "1.11.1"
diff --git a/3/src/main.rs b/3/src/main.rs
new file mode 100644
index 0000000..3347003
--- /dev/null
+++ b/3/src/main.rs
@@ -0,0 +1,88 @@
+use regex::Regex;
+use std::fs::File;
+use std::io::{BufRead, BufReader, Lines};
+use std::time::{Duration, Instant};
+
+// BOILERPLATE
+type InputIter = Lines<BufReader<File>>;
+
+pub fn get_input() -> InputIter {
+    let f = File::open("input").unwrap();
+    let br = BufReader::new(f);
+    br.lines()
+}
+
+fn duration_format(duration: Duration) -> String {
+    match duration.as_secs_f64() {
+        x if x > 1.0 => format!("{:.3}s", x),
+        x if x > 0.010 => format!("{:.3}ms", x * 1e3),
+        x => format!("{:.3}us", x * 1e6),
+    }
+}
+
+fn main() {
+    let input = get_input();
+    let start = Instant::now();
+    let ans1 = problem1(input);
+    let duration1 = start.elapsed();
+    println!("Problem 1 solution: {} [{}]", ans1, duration_format(duration1));
+
+    let input = get_input();
+    let start = Instant::now();
+    let ans2 = problem2(input);
+    let duration2 = start.elapsed();
+    println!("Problem 2 solution: {} [{}]", ans2, duration_format(duration2));
+    println!("Total duration: {}", duration_format(duration1 + duration2));
+}
+
+// PROBLEM 1 solution
+
+fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
+    let mut sum = 0u64;
+    for line in input.map(|i| i.unwrap()) {
+        let re = Regex::new(r"mul\((\d+),(\d+)\)").unwrap();
+        for m in re.captures_iter(&line) {
+            sum += m[1].parse::<u64>().unwrap() * m[2].parse::<u64>().unwrap();
+        }
+    }
+    sum
+}
+
+// PROBLEM 2 solution
+fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
+    let mut sum = 0u64;
+    let mut do_mul = true;
+    for line in input.map(|i| i.unwrap()) {
+        let re = Regex::new(r"(do\(\)|don't\(\)|mul\((\d+),(\d+)\))").unwrap();
+        for m in re.captures_iter(&line) {
+            match &m[1] {
+                "do()" => do_mul = true,
+                "don't()" => do_mul = false,
+                _ if do_mul => sum += m[2].parse::<u64>().unwrap() * m[3].parse::<u64>().unwrap(),
+                _ => {}
+            }
+        }
+    }
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::*;
+    use std::io::Cursor;
+
+    const EXAMPLE1: &str = &"xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))";
+    const EXAMPLE2: &str = &"xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))";
+
+    #[test]
+    fn problem1_example() {
+        let c = Cursor::new(EXAMPLE1);
+        assert_eq!(problem1(c.lines()), 161);
+    }
+
+    #[test]
+    fn problem2_example() {
+        let c = Cursor::new(EXAMPLE2);
+        assert_eq!(problem2(c.lines()), 48);
+    }
+}