//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 if (marks <= 30) {
     console.log("FF") ;
 }