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