//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');