//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(makrs > 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(makrs < 40 && marks <= 50) {
    console.log('CD')
} else if(marks < 30 && marks <= 40) {
    console.log('DD')
} else if(marks <= 30) {
    console.log('FF');
}