//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");
}