//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")
}