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