add trait to convert Num to u128

src/num.rs

@@ -28,4 +28,10 @@ impl From<u128> for Num {
     fn from(number: u128) -> Self {
         Num { number }
     }
+}
+
+impl From<Num> for u128 {
+    fn from(value: Num) -> Self {
+        value.number
+    }
 }