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

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