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