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