//Do not declare variable marks.
//Write your code below this line.

if (marks > 90){
    console.log('AA');
}
else if (80 < marks && marks <= 90){
    console.log('AB');
}
else if (70 < marks && marks <= 80){
    console.log('BB');
}
else if (60 < marks && marks <= 70){
    console.log('BC');
}
else if (50 < marks && marks <= 60){
    console.log('CC');
}
else if (40 < marks && marks <= 50){
    console.log('CD');
}
else if (30 < marks && marks <= 40){
    console.log('DD');
}
else if (marks <= 30){
    console.log('FF');
}