//Do not declare variable marks.
//Write your code below this line.
if (marks > 90) console.log('AA');
else if (marks > 80) console.log('AB');
else if (marks > 70) console.log('BB');
else if (marks > 60) console.log('BC');
else if (marks > 50) console.log('CC');
else if (marks > 40) console.log('CD');
else if (marks > 30) console.log('DD');
else console.log('FF');