//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');
}