#!/bin/sh

if [ $# -ne 3 ]; then
    echo "Usage: ./seq.sh FIRST INCREMENT LAST" 1>&2
    exit 1
fi

if [ "$2" -eq 0 ]; then
    exit 1
fi

if [ "$1" -eq "$3" ]; then
    echo "$1"
    exit 0
fi

if [ "$1" -lt "$3" ]; then
    [ 0 -gt "$2" ] && exit 1
    i="$1"
    while [ "$3" -ge "$i" ]; do
        echo "$i"
        i=$(($i + $2))
    done
    exit 0
fi

[ "$2" -gt 0 ] && exit 1
i="$1"
while [ "$i" -ge "$3" ]; do
    echo "$i"
    i=$(($i + $2))
done
exit 0