//Do not declare variable marks.
//Write your code below this line.
if(marks > 90){
    console.log("AA");
}
else if(marks > 80 <= 90){
    console.log("AB");
}
else if(marks > 70 <= 80){
    console.log("BB");
}
else if(marks > 60 <= 70){
    console.log("BC");
}
else if(marks > 50 <= 60){
    console.log("CC");
}
else if(marks > 40 <= 50){
    console.log("CD");
}
else if(marks > 30 <= 40){
    console.log("DD");
}
else if(marks <= 30){
    console.log("FF");
}