//Do not declare variable marks.
//Write your code below this line.
if(marks > 90) {
    console.log('AA');
}
else if(marks > 80) {
    console.log('AB');
}
else if(marks > 70) {
    console.log('BB');   
}
else if(marks > 60) {
    console.log('BC');   
}
else if(marks > 50) {
    console.log('CC');   
}
else if(marks > 40) {
    console.log('CD');   
}
else if(marks > 30) {
    console.log('DD');   
}
else {
    console.log('FF');
}