summation.zsh

#!/usr/bin/env zsh

numbers=($(<${1}))

for n in {1..${#numbers}..2}; do
  first=${numbers[n]}
  second=${numbers[$(( n + 1 ))]}

  sum=0
  for i in {${first}..${second}}; do
    sum=$(( ${sum} + i ))
  done

  print ${sum}
done