give a python code for Grading using nested if else statement with no errors and it should be ;like getting input from the user

$90-100--------$ O

$80-89---------$ A$+$

$70-79----------$A

$60-69---------$B$+$

$50-59---------$B

$40-49---------$C

$30-39---------$P

$<30----------$F