//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");
    }