//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");
}