//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");
}