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

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