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

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