diff --git a/Week-02/Day-09_Trapping-Rain-Water/day9/Cargo.toml b/Week-02/Day-09_Trapping-Rain-Water/day9/Cargo.toml
new file mode 100644
index 0000000..48c42be
--- /dev/null
+++ b/Week-02/Day-09_Trapping-Rain-Water/day9/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "day9"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/Week-02/Day-09_Trapping-Rain-Water/day9/src/lib.rs b/Week-02/Day-09_Trapping-Rain-Water/day9/src/lib.rs
new file mode 100644
index 0000000..e0464cc
--- /dev/null
+++ b/Week-02/Day-09_Trapping-Rain-Water/day9/src/lib.rs
@@ -0,0 +1,26 @@
+pub fn trap(heights: Vec<u8>) -> u16 {
+    let maxh = heights.iter().max().cloned().unwrap_or(0);
+    let mut water: u16 =
+        maxh as u16 * heights.len() as u16 - heights.iter().map(|x| *x as u16).sum::<u16>();
+    let mut maxt;
+
+    maxt = 0;
+    for h in heights.iter() {
+        maxt = std::cmp::max(maxt, *h);
+        if maxt == maxh {
+            break;
+        }
+        water -= maxh as u16 - maxt as u16;
+    }
+
+    maxt = 0;
+    for h in heights.iter().rev() {
+        maxt = std::cmp::max(maxt, *h);
+        if maxt == maxh {
+            break;
+        }
+        water -= maxh as u16 - maxt as u16;
+    }
+
+    water
+}
diff --git a/Week-02/Day-09_Trapping-Rain-Water/day9/src/main.rs b/Week-02/Day-09_Trapping-Rain-Water/day9/src/main.rs
new file mode 100644
index 0000000..d043dc6
--- /dev/null
+++ b/Week-02/Day-09_Trapping-Rain-Water/day9/src/main.rs
@@ -0,0 +1,24 @@
+use std::io::{self, Write};
+
+use day9::trap;
+
+fn main() {
+    let mut buffer = String::new();
+
+    print!("Insert space separated heights: ");
+    io::stdout().flush().expect("Failed to flush stdout.");
+
+    io::stdin()
+        .read_line(&mut buffer)
+        .expect("Failed to read from input.");
+
+    let heights = buffer
+        .trim()
+        .split(' ')
+        .filter(|x| !x.is_empty())
+        .map(|x| x.parse().expect("A not number has been found"))
+        .collect();
+
+    let water = trap(heights);
+    println!("{}", water);
+}
diff --git a/Week-02/Day-09_Trapping-Rain-Water/day9/tests/exaples.rs b/Week-02/Day-09_Trapping-Rain-Water/day9/tests/exaples.rs
new file mode 100644
index 0000000..df9ceba
--- /dev/null
+++ b/Week-02/Day-09_Trapping-Rain-Water/day9/tests/exaples.rs
@@ -0,0 +1,11 @@
+use day9::trap;
+
+#[test]
+fn exaple1() {
+    assert_eq!(trap([0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1].to_vec()), 6);
+}
+
+#[test]
+fn exaple2() {
+    assert_eq!(trap([4, 2, 0, 3, 2, 5].to_vec()), 9);
+}