//Do not declare variable marks.
//Write your code below this line.

if(marks >= 90){
    console.log("AA");
}
else if(mark >= 80){
    console.log("AB");
}
else if(mark >= 70){
    console.log("BB");
}
else if(mark >= 60){
    console.log("BC");
}
else if(mark >= 50){
    console.log("CC");
}
else if(mark >= 40){
    console.log("CD");
}
else if(mark >= 30){
    console.log("DD");
}
else if(mark >= 20){
    console.log("FF");
}