diff --git a/day15/Cargo.lock b/day15/Cargo.lock
new file mode 100644
index 0000000..2473428
--- /dev/null
+++ b/day15/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day15"
+version = "0.1.0"
diff --git a/day15/Cargo.toml b/day15/Cargo.toml
new file mode 100644
index 0000000..f52c8dc
--- /dev/null
+++ b/day15/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day15"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/day15/input.txt b/day15/input.txt
new file mode 100644
index 0000000..98b310f
--- /dev/null
+++ b/day15/input.txt
@@ -0,0 +1,33 @@
+Sensor at x=2899860, y=3122031: closest beacon is at x=2701269, y=3542780
+Sensor at x=1836719, y=1116779: closest beacon is at x=2037055, y=2000000
+Sensor at x=3995802, y=2706630: closest beacon is at x=3944538, y=3053285
+Sensor at x=2591204, y=2008272: closest beacon is at x=2597837, y=2509170
+Sensor at x=2546593, y=1538222: closest beacon is at x=2037055, y=2000000
+Sensor at x=252214, y=61954: closest beacon is at x=1087565, y=-690123
+Sensor at x=950, y=1106672: closest beacon is at x=-893678, y=1276864
+Sensor at x=1349445, y=1752783: closest beacon is at x=2037055, y=2000000
+Sensor at x=3195828, y=3483667: closest beacon is at x=3334657, y=3531523
+Sensor at x=2057761, y=2154359: closest beacon is at x=2037055, y=2000000
+Sensor at x=2315350, y=3364640: closest beacon is at x=2701269, y=3542780
+Sensor at x=327139, y=2426600: closest beacon is at x=-88420, y=3646947
+Sensor at x=3943522, y=2854345: closest beacon is at x=3944538, y=3053285
+Sensor at x=3358620, y=516881: closest beacon is at x=3260516, y=2246079
+Sensor at x=1788376, y=8679: closest beacon is at x=1087565, y=-690123
+Sensor at x=3344883, y=3537985: closest beacon is at x=3334657, y=3531523
+Sensor at x=2961064, y=2697125: closest beacon is at x=2597837, y=2509170
+Sensor at x=3780090, y=2093546: closest beacon is at x=3260516, y=2246079
+Sensor at x=3291917, y=3398703: closest beacon is at x=3334657, y=3531523
+Sensor at x=3999864, y=2998005: closest beacon is at x=3944538, y=3053285
+Sensor at x=2919272, y=3732950: closest beacon is at x=2701269, y=3542780
+Sensor at x=2057404, y=2947435: closest beacon is at x=2037055, y=2000000
+Sensor at x=1072126, y=645784: closest beacon is at x=1087565, y=-690123
+Sensor at x=3549465, y=2554712: closest beacon is at x=3260516, y=2246079
+Sensor at x=3550313, y=3121694: closest beacon is at x=3944538, y=3053285
+Sensor at x=3405149, y=3483630: closest beacon is at x=3334657, y=3531523
+Sensor at x=2600212, y=3961193: closest beacon is at x=2701269, y=3542780
+Sensor at x=1102632, y=3932527: closest beacon is at x=-88420, y=3646947
+Sensor at x=67001, y=3506079: closest beacon is at x=-88420, y=3646947
+Sensor at x=3994250, y=3975025: closest beacon is at x=3944538, y=3053285
+Sensor at x=3019750, y=2125144: closest beacon is at x=3260516, y=2246079
+Sensor at x=3282319, y=3656404: closest beacon is at x=3334657, y=3531523
+Sensor at x=2797371, y=3645126: closest beacon is at x=2701269, y=3542780
diff --git a/day15/src/main.rs b/day15/src/main.rs
new file mode 100644
index 0000000..1501603
--- /dev/null
+++ b/day15/src/main.rs
@@ -0,0 +1,78 @@
+use std::env;
+use std::fs::File;
+use std::io::{BufReader, BufRead};
+use std::cmp::{min, max};
+use std::collections::HashSet;
+
+fn parse_num(s: &[u8]) -> (i64, usize) {
+    let mut num: i64 = 0;
+    let negative = s[0] == '-' as u8;
+    let start = if negative {1} else {0};
+    let mut len = if negative {1} else {0};
+
+    for i in start..s.len() {
+        if s[i].is_ascii_digit() {
+            num = num*10 + (s[i] as i64 - '0' as i64);
+            len += 1;
+        } else {
+            break;
+        }
+    }
+    (if negative {-num} else {num}, len)
+}
+
+fn combine(ranges: &mut Vec<(i64, i64)>, l: i64, r: i64) {
+    for (l0, r0) in ranges.iter_mut() {
+        if *l0 <= r && l <= *r0 {
+            *l0 = min(*l0, l);
+            *r0 = max(*r0, r);
+            return;
+        }
+    }
+    ranges.push((l, r));
+}
+
+fn main() {
+    let file = File::open(&env::args().nth(1).expect("input")).expect("io err");
+    let lines = BufReader::new(file).lines();
+    let mut sensors: Vec<(i64, i64, u64)> = Vec::new();
+    let mut beacons: HashSet<(i64, i64)> = HashSet::new();
+    for line in lines.flatten() {
+        let l_bytes = line.as_bytes();
+        let (sx, e1) = parse_num(&l_bytes[12..]);
+        let (sy, e2) = parse_num(&l_bytes[12 + e1 + 4..]);
+        let (bx, e3) = parse_num(&l_bytes[12 + e1 + 4 + e2 + 25..]);
+        let (by, _) = parse_num(&l_bytes[12 + e1 + 4 + e2 + 25 + e3 + 4..]);
+        sensors.push((sx, sy, ((bx - sx).abs() + (by - sy).abs()) as u64));
+        beacons.insert((bx, by));
+    }
+    sensors.sort_by_key(|(x, _, _)| *x);
+    println!("{:?}", sensors);
+    println!("{:?}", beacons);
+
+    let target_y = &env::args().nth(2).expect("line").parse::<i64>().unwrap();
+    let mut coverage: Vec<(i64, i64)> = Vec::new();
+    for (sx, sy, range) in sensors {
+        let clip = (range as i64) - (sy - target_y).abs();
+        if clip < 0 {
+            continue;
+        }
+        let startx = sx - clip;
+        let endx = sx + clip;
+        combine(&mut coverage, startx, endx);
+         
+    }
+    println!("{:?}", coverage);
+
+    let mut sum = 0;
+    for (l, r) in coverage {
+        let mut overlap = 0;
+        for (bx, by) in &beacons {
+            if *by == *target_y && l <= *bx && r >= *bx {
+                overlap += 1;
+            }
+        }
+        sum += r - l + 1 - overlap;
+    }
+    println!("answer: {:?}", sum);
+}
diff --git a/day15/test.txt b/day15/test.txt
new file mode 100644
index 0000000..a612424
--- /dev/null
+++ b/day15/test.txt
@@ -0,0 +1,14 @@
+Sensor at x=2, y=18: closest beacon is at x=-2, y=15
+Sensor at x=9, y=16: closest beacon is at x=10, y=16
+Sensor at x=13, y=2: closest beacon is at x=15, y=3
+Sensor at x=12, y=14: closest beacon is at x=10, y=16
+Sensor at x=10, y=20: closest beacon is at x=10, y=16
+Sensor at x=14, y=17: closest beacon is at x=10, y=16
+Sensor at x=8, y=7: closest beacon is at x=2, y=10
+Sensor at x=2, y=0: closest beacon is at x=2, y=10
+Sensor at x=0, y=11: closest beacon is at x=2, y=10
+Sensor at x=20, y=14: closest beacon is at x=25, y=17
+Sensor at x=17, y=20: closest beacon is at x=21, y=22
+Sensor at x=16, y=7: closest beacon is at x=15, y=3
+Sensor at x=14, y=3: closest beacon is at x=15, y=3
+Sensor at x=20, y=1: closest beacon is at x=15, y=3