//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");