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

if(marks>90){
    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");
};