Use a common macro to instrument each part

crates/common/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "common"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

crates/common/src/lib.rs

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+use std::time::Instant;
+
+#[macro_export]
+macro_rules! instrument {
+    ($part1:expr, $part2:expr) => {
+        let mut now = Instant::now();
+        println!("Part 1: {}", $part1);
+        println!("(elapsed: {:?})", now.elapsed());
+        now = Instant::now();
+        println!("");
+        println!("Part 2: {}", $part2);
+        println!("(elapsed: {:?})", now.elapsed());
+    };
+}