//Do not declare variable marks.
//Write your code below this line.

if(marks > 90) {
    console.log("AA");
}
else if (marks >80 && marks <= 70){
     console.log("AB");
}
else if(marks >70 && marks <= 60){
     console.log("BB");
}
else if (marks >60 && marks <= 50){
     console.log("BC");
}
else if(marks >50 && marks <= 40){
     console.log("CC");
}
else if (marks >40 && marks <= 30){
     console.log("CD");
}
else if(marks >30 && marks <= 40){
     console.log("DD");
}
else if (marks < 30){
     console.log("FF");
}