//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')
}