//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 if (marks >= 30 || marks < 40) {
    console.log("FF");
}