//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 if(marks <= 30){
    console.log("FF");
}