diff --git a/add/Cargo.lock b/add/Cargo.lock
index efe4e14..867106b 100644
--- a/add/Cargo.lock
+++ b/add/Cargo.lock
@@ -2,6 +2,10 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "add_one"
+version = "0.1.0"
+
 [[package]]
 name = "adder"
 version = "0.1.0"
diff --git a/add/Cargo.toml b/add/Cargo.toml
index c5ea8e5..1448801 100644
--- a/add/Cargo.toml
+++ b/add/Cargo.toml
@@ -2,4 +2,5 @@
 
 members = [
     "adder",
+    "add_one",
 ]
diff --git a/add/add_one/Cargo.toml b/add/add_one/Cargo.toml
new file mode 100644
index 0000000..dcfb7f9
--- /dev/null
+++ b/add/add_one/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "add_one"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
diff --git a/add/add_one/src/lib.rs b/add/add_one/src/lib.rs
new file mode 100644
index 0000000..b0bb869
--- /dev/null
+++ b/add/add_one/src/lib.rs
@@ -0,0 +1,3 @@
+pub fn add_one(x: i32) -> i32 {
+    x + 1
+}