//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');
}