//Do not declare variable marks.
//Write your code below this line.
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");
}