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

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