diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..142c814
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "aoc21"
+version = "0.1.0"
diff --git a/input/day1.txt b/input/day1.txt
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diff --git a/src/day1.rs b/src/day1.rs
new file mode 100644
index 0000000..29ea87e
--- /dev/null
+++ b/src/day1.rs
@@ -0,0 +1,43 @@
+pub fn day1() {
+    // let input = r#"199
+    // 200
+    // 208
+    // 210
+    // 200
+    // 207
+    // 240
+    // 269
+    // 260
+    // 263"#;
+    let input = include_str!("../input/day1.txt");
+
+    let ints = input
+        .trim()
+        .lines()
+        .map(|s| s.trim().parse::<i32>().unwrap());
+
+    let mut iter = ints.clone();
+    let mut prev: i32 = iter.next().unwrap();
+    let mut count = 0;
+    for cur in iter {
+        if cur > prev {
+            count += 1;
+        }
+        prev = cur;
+    }
+
+    println!("count: {}", count);
+
+    let mut iter = ints.clone().zip(ints.clone().skip(1).zip(ints.skip(2)));
+    let first = iter.next().unwrap();
+    let mut prev_sum = first.0 + first.1 .0 + first.1 .1;
+    let mut new_count = 0;
+    for (a, (b, c)) in iter {
+        let sum = a + b + c;
+        if sum > prev_sum {
+            new_count += 1;
+        }
+        prev_sum = sum;
+    }
+    println!("new_count: {}", new_count);
+}
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..8b806eb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,5 @@
+mod day1;
+
 fn main() {
-    println!("Hello, world!");
+    day1::day1();
 }