#!/bin/awk -f
# chain-add: A chain addition generator
# Thanks to Justin Parrott for the inspiration
BEGIN {
  printf "Enter number of rounds: ";
  getline rounds < "/dev/stdin";
  printf "Enter key: ";
  getline key < "/dev/stdin";
  split(key, num, "");
  len = length(num);

  for (i = 1; i <= rounds; i++) {
    num[len + i] = ((num[i] + num[i + 1]) % 10);
    printf num[len + i]
  };

print
}