//Do not declare variable marks.
//Write your code below this line.
if (marks>90) {
    console.lof("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 if (30>marks) {
    console.log("FF")
}