//Do not declare variable marks.
//Write your code below this line.
if(marks>90){
    console.log("AA")
}
else if (80<marks<=90){
    console.log("AB")
}
else if (70<marks<=80){
    console.log("BB")
}
else if (60<marks<=70){
    console.log("BC")
}
else if (50<marks<=60){
    console.log("CC")
}
else if (40<marks<=50){
    console.log("CD")
}
else if (30<marks<=40){
    console.log("DD")
}
else if (marks<=30){
    console.log("FF")
}