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