if(marks > 90){
    console.log("AA");
}
if(marks > 80 && marks <=90){
    console.log("AB");
}
if(marks > 70 && marks <=80){
    console.log("BB");
}
if(marks > 60 && marks <=70){
    console.log("BC");
}
if(marks > 50 && marks <=60){
    console.log("CC");
}
if(marks > 40 && marks <=50){
    console.log("CD");
}
if(marks > 30 && marks <=40){
    console.log("DD");
}
if(marks <= 30){
    console.log("FF");
}

//Do not declare variable marks.
//Write your code below this line.