fn process(data: &[u8]) -> u64 {
    data.iter().map(|&x| x as u64).sum()
}

fn main() {
    let data = vec![0u8; 1024*1024*1024];
    let chunk_size = 1024;

    let mut reversed = Vec::new();
    let mut sum = 0;
    for cur_data in data.chunks(chunk_size) {
        reversed.truncate(0);
        reversed.extend(cur_data.iter().rev());
        sum += process(&reversed);
    }
    println!("{}", sum);
}