//Do not declare variable marks.
//Write your code below this line.
if(marks>90){
    console.log("AA");
}else if(90>marks>80){
    console.log("AB");
}else if(80>marks>70){
    console.log("BB");
}else if(70>marks>60){
    console.log("BC");
}else if(60>marks>50){
    console.log("CC");
}else if(50>marks>40){
    console.log("CD");
}else if(40>marks>30){
    console.log("DD");
}else{
    console.log("FF");
}