//Do not declare variable marks.
//Write your code below this line.
value = "";

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