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

console.log(score);