fn first_improvement(input: &[u8]) -> i32 {
    let mut idx = 0;
    let len = input.len();
    let mut cursor: i32 = 50;
    let mut clock_crosses: i32 = 0;

    while idx < len {
        // Direction: single byte comparison (if it's not left then it's right..)
        let is_left = unsafe { *input.get_unchecked(idx) } == b'L';
        idx += 1;

        // Parse first digit(we know there's always at least
        // one digit after the first L/R byte): ASCII '0'-'9' maps to 0x30-0x39
        // Subtracting b'0' (0x30) converts ASCII digit to integer
        let mut num = unsafe { (*input.get_unchecked(idx) - b'0') as i32 };
        idx += 1;

        // Parse remaining digits until we hit a non-digit
        while idx < len {
            let b = unsafe { *input.get_unchecked(idx) };
            // Newline (0x0A) and other control chars are < 0x30 ('0')
            // This single comparison detects end-of-number
            if b < 0x30 {
                idx += 1;  // Skip the newline
                break;
            }
            // Standard decimal parsing: num = num * 10 + digit
            num = num * 10 + (b - 0x30) as i32;
            idx += 1;
        }

        // Same logic as the base implementation: the rest is identical
        let quotient = num / 100;
        let rem = num % 100;

        if is_left {
            let raw = cursor - rem;
            let new_cursor = raw + (100 & (raw >> 31));
            let crosses_extra = (cursor != 0 && cursor < rem) as i32;
            clock_crosses += quotient + crosses_extra + (new_cursor == 0) as i32;
            cursor = new_cursor;
        } else {
            let raw = cursor + rem;
            let overflow = (raw >= 100) as i32;
            let new_cursor = raw - 100 * overflow;
            let crosses_extra = (cursor != 0 && new_cursor != 0 && overflow != 0) as i32;
            clock_crosses += quotient + crosses_extra + (new_cursor == 0) as i32;
            cursor = new_cursor;
        }
    }

    clock_crosses
}

; Byte-level: specialized, no checks needed
lea r9d, [r9 + 4*r9]       ; num * 5
add r11b, -48              ; digit = byte - '0'
lea r9d, [r11 + 2*r9]      ; num = num*10 + digit