//Do not declare variable marks.
//Write your code below this line.
function checkMarks(marks){
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");
}
    return marks;
}
checkMarks(100);