//Do not declare variable marks.
//Write your code below this line.
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");
}