#!/bin/sh

if [ $# -ne 1 ]; then
  echo "usage: square num" >&2
  exit 1
elif [ "$1" -lt 0 ]; then
  exit 0
elif [ "$1" -gt 0 ]; then
  echo "$1"  | awk '{ for (i = 0; i <= $1; i++) print i, i*i }'
else
  echo "0 0"
fi