//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")
}