diff --git a/src/alphametics.rs b/src/alphametics.rs
index 48ce1d2..e6c93de 100644
--- a/src/alphametics.rs
+++ b/src/alphametics.rs
@@ -3,7 +3,7 @@ use std::collections::{HashMap, HashSet};
 use itertools::Itertools;
 
 pub fn solve(input: &str) -> Option<HashMap<char, u8>> {
-    let mut iter = input.clone().split("==");
+    let mut iter = input.split("==");
 
     let sum: Vec<&str> = iter.next().unwrap().split("+").map(|x| x.trim()).collect();
     let answer: &str = iter.next().unwrap().trim();
diff --git a/src/isbn_verifier.rs b/src/isbn_verifier.rs
index c500b0b..519a50a 100644
--- a/src/isbn_verifier.rs
+++ b/src/isbn_verifier.rs
@@ -1,4 +1,12 @@
 /// Determines whether the supplied string is a valid ISBN number
 pub fn is_valid_isbn(isbn: &str) -> bool {
-    todo!("Is {isbn:?} a valid ISBN number?");
+    if isbn.is_empty() {
+        return false;
+    }
+
+    let isbn_digit: Vec<_> = isbn.to_string().chars().filter(|c| c.is_ascii_digit()).collect();
+    println!("{:?}", isbn_digit);
+
+    true
+    // todo!("Is {isbn:?} a valid ISBN number?");
 }
diff --git a/src/main.rs b/src/main.rs
index 2a778e4..1c5c486 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,4 @@
+use exercism::isbn_verifier;
 fn main() {
-
+    isbn_verifier::is_valid_isbn("3-598-21507-X");
 }