//Do not declare variable marks.
//Write your code below this line.
if (marks > 90) console.log("AA");
else if (90 >= marks > 80) console.log("AA");
else if (80 >= marks > 70) console.log("AB");
else if (70 >= marks > 60) console.log("BB");
else if (60 >= marks > 50) console.log("BC");
else if (50 >= marks > 40) console.log("CC");
else if (40 >= marks > 30) console.log("DD");
else if (marks < 30) console.log("FF");