//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{
    console.log('FF');
}