//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');
}