//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");
    }