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