//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");
}