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