diff --git a/Cargo.lock b/Cargo.lock
index 266fa11..07686dd 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -7,6 +7,7 @@ name = "aoc"
 version = "0.1.0"
 dependencies = [
  "dotenv",
+ "itertools",
  "pico-args",
  "reqwest",
 ]
@@ -75,6 +76,12 @@ version = "0.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77c90badedccf4105eca100756a0b1289e191f6fcbdadd3cee1d2f614f97da8f"
 
+[[package]]
+name = "either"
+version = "1.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "90e5c1c8368803113bf0c9584fc495a58b86dc8a29edbf8fe877d21d9507e797"
+
 [[package]]
 name = "encoding_rs"
 version = "0.8.31"
@@ -311,6 +318,15 @@ version = "2.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f88c5561171189e69df9d98bcf18fd5f9558300f7ea7b801eb8a0fd748bd8745"
 
+[[package]]
+name = "itertools"
+version = "0.10.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.4"
diff --git a/Cargo.toml b/Cargo.toml
index 7394066..d2a904a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@ default-run = "aoc"
 [dependencies]
 # framework
 dotenv = "0.15.0"
+itertools = "0.10.5"
 pico-args = "0.5.0"
 reqwest = { version = "0.11.13", features = ["blocking"] }
 # for solving