fn main() {
  let vec1 = vec![
    "1234567890",
    "qwertyuiop",
    "asdfghjkl",
    "zxcvbnm",
  ];
  let ss = vec1.iter()
    .fold(String::new(), |sum, item| sum + item);

  let word_length = 4;
  let iterate_to = ss.chars().count()+1-word_length;
  for j in 0..iterate_to {
     let w: String = ss.chars()
       .skip(j)
       .take(word_length)
       .collect();
     println!("{:?}",w);
  }
}