//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{
   console.log("FF");
        }