//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{
    console.log("FF");
}