fn main() {
    let mut buffer = String::with_capacity(65 * 500_000);

    let mut c_buf = [0u8; 65];
    loop {
        unsafe {
            gets(c_buf.as_mut_ptr());
        }
        if c_buf[0] == b'0' {
            buffer.push('0');
            break;
        }
        for &letter in c_buf.iter() {
            if !(letter == b' '
                || (letter >= b'0' && letter <= b'9')
                || (letter >= b'A' && letter <= b'Z'))
            {
                break;
            }
            buffer.push(letter as char);
        }
        buffer.push('\n');
    }

...