//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>=50){
    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{
    console.log("FF")
}