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

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