echo "enter first number"
read f_num

echo "enter second number"
read s_num

echo "sum = `expr $f_num + $s_num`"
echo "sub = `expr $f_num - $s_num`"
echo "mul = `expr $f_num \* $s_num`"


if [ $s_num -gt 0 ]; then
   echo "div = `expr $f_num / $s_num`"
   echo "mod = `expr $f_num % $s_num`"
else
    echo "div = not possible"
    echo "mod = not possible"
fi