diff --git a/calculate/src/optimized.rs b/calculate/src/optimized.rs
index 1d116f3..2805729 100644
--- a/calculate/src/optimized.rs
+++ b/calculate/src/optimized.rs
@@ -116,15 +116,12 @@ pub(crate) fn run(args: Args) -> Result<()> {
     Ok(())
 }
 
-fn parse_temp(temp: &[u8]) -> i64 {
-    let dec = |b| (b - b'0') as i64;
-    let (sign, a, b, c) = match temp {
-        [b'-', a, b, b'.', c] => (-1, dec(a), dec(b), dec(c)),
-        [b'-', b, b'.', c] => (-1, 0, dec(b), dec(c)),
-        [a, b, b'.', c] => (1, dec(a), dec(b), dec(c)),
-        [b, b'.', c] => (1, 0, dec(b), dec(c)),
-        _ => panic!("bad input"),
-    };
+fn parse_temp(input: &[u8], sep_pos: usize, nl_pos: usize) -> i64 {
+    let sign = 2 * (unsafe { *input.get_unchecked(sep_pos + 1) } != b'-') as i64 - 1;
+    let a_byte = unsafe { *input.get_unchecked(nl_pos - 4) };
+    let a = (b'0' <= a_byte && a_byte <= b'9') as i64 * a_byte.wrapping_sub(b'0') as i64;
+    let b = (unsafe { *input.get_unchecked(nl_pos - 3) } - b'0') as i64;
+    let c = (unsafe { *input.get_unchecked(nl_pos - 1) } - b'0') as i64;
     sign * (a * 100 + b * 10 + c)
 }
 
@@ -134,16 +131,15 @@ fn chunk(input: &[u8], pb: ProgressBar) -> Result<HashMap<&[u8], Data>> {
     let mut start = 0;
     let mut last_pb_update: usize = 0;
     let mut iter = memchr2_iter(b'\n', b';', input);
-    while let Some(split) = iter.next() {
-        if input[split] != b';' {
-            start = split + 1;
+    while let Some(sep_pos) = iter.next() {
+        if unsafe { *input.get_unchecked(sep_pos) } != b';' {
+            start = sep_pos + 1;
             continue;
         }
-        let pos = iter.next().context("bad input")?;
-        let city = &input[start..split];
-        let temperature = &input[split + 1..pos];
-        start = pos + 1;
-        let temperature = parse_temp(temperature);
+        let nl_pos = unsafe { iter.next().unwrap_unchecked() };
+        let city = unsafe { input.get_unchecked(start..sep_pos) };
+        let temperature = parse_temp(input, sep_pos, nl_pos);
+        start = nl_pos + 1;
         let entry = data.entry(city);
         entry
             .and_modify(|data| {
@@ -158,12 +154,12 @@ fn chunk(input: &[u8], pb: ProgressBar) -> Result<HashMap<&[u8], Data>> {
                 sum: temperature,
                 count: 1,
             });
-        let last_pb_update_delta = pos - last_pb_update;
+        let last_pb_update_delta = nl_pos - last_pb_update;
         if last_pb_update_delta >= 10_000_000 {
-            pb.inc(last_pb_update_delta.try_into()?);
-            last_pb_update = pos;
+            pb.inc(last_pb_update_delta as u64);
+            last_pb_update = nl_pos;
         }
     }
-    pb.inc((input.len() - last_pb_update).try_into()?);
+    pb.inc((input.len() - last_pb_update) as u64);
     Ok(data)
 }