//Do not declare variable marks.
//Write your code below this line.

var result = 'FF';
if (marks > 90) {
    result = 'AA'
} else if (marks > 80) {
    result = 'AB'
} else if (marks > 70) {
    result = 'BB'
} else if (marks > 60) {
    result = 'BC'
} else if (marks > 50) {
    result = 'CC'
} else if (marks > 40) {
    result = 'CD'
} else if (marks > 30) {
    result = 'DD'
}

console.log(result);