//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 if (marks>0){
    console.log("FF");
}