//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
{
    console.log("FF");
}