//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")
    }
}