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