//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 && <= 60){
    console.log('CC');
};
else if (marks > 40 && <=50){
    console.log('CD');
};
else if (marks > 30 <= 40) {
    console.log('DD');
};
else if (marks <= 30){ 
    console.log('FF')
};