diff --git a/README.md b/README.md
index bd61e01..9b03225 100644
--- a/README.md
+++ b/README.md
@@ -14,3 +14,7 @@ cargo run
 | a | b |
 |---|---|
 | 1 | 2 |
+
+## Multiply
+
+Now supports mul.
diff --git a/src/core/lib.rs b/src/core/lib.rs
index a998b78..039d6b0 100644
--- a/src/core/lib.rs
+++ b/src/core/lib.rs
@@ -12,3 +12,6 @@ mod tests {
 pub fn sub(a: i32, b: i32) -> i32 {
     a - b
 }
+pub fn mul(a: i32, b: i32) -> i32 {
+    a * b
+}