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

if(marks > 90){
    console.log('AA');
}else if(marks <= 90 && marks > 80){
    console.log('AB');
}else if(marks <= 80 && marks > 70){
    console.log('BB');
}else if(marks <= 70 && marks > 60){
    console.log('BC');
}else if(marks <= 60 && marks > 50){
    console.log('CC');
}else if(marks <= 50 && marks > 40){
    console.log('CD');
}else if(marks <= 40 && marks > 30){
    console.log('DD');
}else {
    console.log('FF');
}