Write a shell script to check given year is leap year or not. - OS

echo "enter any year"
read num
if [ `expr $num % 4` -eq 0 ]
then
if [ `expr $num % 100` -eq 0 -a `expr $num % 400` -ne 0 ]
then
echo "Not a leap year"
else
echo "Leap year "
fi
else
echo "Not a leap year"
fi