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diff --git a/exercises/13_error_handling/errors5.rs b/exercises/13_error_handling/errors5.rs
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+++ b/exercises/13_error_handling/errors5.rs
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+// errors5.rs
+//
+// This program uses an altered version of the code from errors4.
+//
+// This exercise uses some concepts that we won't get to until later in the
+// course, like `Box` and the `From` trait. It's not important to understand
+// them in detail right now, but you can read ahead if you like. For now, think
+// of the `Box<dyn ???>` type as an "I want anything that does ???" type, which,
+// given Rust's usual standards for runtime safety, should strike you as
+// somewhat lenient!
+//
+// In short, this particular use case for boxes is for when you want to own a
+// value and you care only that it is a type which implements a particular
+// trait. To do so, The Box is declared as of type Box<dyn Trait> where Trait is
+// the trait the compiler looks for on any value used in that context. For this
+// exercise, that context is the potential errors which can be returned in a
+// Result.
+//
+// What can we use to describe both errors? In other words, is there a trait
+// which both errors implement?
+//
+// Execute `rustlings hint errors5` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+use std::error;
+use std::fmt;
+use std::num::ParseIntError;
+
+// TODO: update the return type of `main()` to make this compile.
+fn main() -> Result<(), Box<dyn ???>> {
+    let pretend_user_input = "42";
+    let x: i64 = pretend_user_input.parse()?;
+    println!("output={:?}", PositiveNonzeroInteger::new(x)?);
+    Ok(())
+}
+
+// Don't change anything below this line.
+
+#[derive(PartialEq, Debug)]
+struct PositiveNonzeroInteger(u64);
+
+#[derive(PartialEq, Debug)]
+enum CreationError {
+    Negative,
+    Zero,
+}
+
+impl PositiveNonzeroInteger {
+    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
+        match value {
+            x if x < 0 => Err(CreationError::Negative),
+            x if x == 0 => Err(CreationError::Zero),
+            x => Ok(PositiveNonzeroInteger(x as u64)),
+        }
+    }
+}
+
+// This is required so that `CreationError` can implement `error::Error`.
+impl fmt::Display for CreationError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let description = match *self {
+            CreationError::Negative => "number is negative",
+            CreationError::Zero => "number is zero",
+        };
+        f.write_str(description)
+    }
+}
+
+impl error::Error for CreationError {}