//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");
}