//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 {
    console.log("FF");
}