diff --git a/src/days/d9.rs b/src/days/d9.rs
index 13a5341..b1d3a9e 100644
--- a/src/days/d9.rs
+++ b/src/days/d9.rs
@@ -3,25 +3,25 @@ use crate::prelude::*;
 pub type I = SS;
 pub type O = usize;
 
-fn _expand (mut data: impl Iterator<Item = char>) -> String {
-    let mut stack = String::new();
+fn _expand (mut data: impl Iterator<Item = char>) -> O {
+    let mut stack = 0;
 
-    data.by_ref().take_while(|e| *e != '(').for_each(|c| stack.push(c));
+    data.by_ref().take_while(|e| *e != '(').for_each(|_| stack += 1);
 
     let a = data.by_ref().take_while(|c| *c != ')').collect::<String>();
     let Some((len, times)) = a.split_once('x') else { return stack };
     let len = len.parse::<usize>().unwrap();
-    let mut taken = data.by_ref().take(len).filter(|e| !e.is_control() && !e.is_whitespace()).collect::<String>();
+    let taken = data.by_ref().take(len).filter(|e| !e.is_control() && !e.is_whitespace()).collect::<String>();
 
-    while let Some(p) = taken.find("(") {
-        let new = format!("{}{}", &taken[..p], _expand(taken[p..].chars()));
-        // println!("{:?} -> {:?}", taken, new);
-        taken = new;
-    }
+    let t = if let Some(p) = taken.find("(") {
+        p + _expand(taken[p..].chars())
+    } else {
+        taken.len()
+    };
 
     let times = times.parse::<usize>().unwrap();
-    stack.push_str(&taken.repeat(times));
-    stack.push_str(&_expand(data));
+    stack += t * times;
+    stack += _expand(data);
 
     stack
 }
@@ -53,7 +53,7 @@ fn _silver (data: I) -> O {
 
 fn _gold (data: I) -> O {
     let stack = _expand(data.trim().chars());
-    stack.len()
+    stack
 }
 
 #[cfg(test)]