//Do not declare variable marks.
//Write your code below this line.
if (marks>90)
    {
        console.log("AA");
    }
else
    if (marks>80 || marks<=90)
    {
        console.log("AB");
    }
else
    if (marks>70 || marks<=80)
    {
        console.log("BB");
    }
else
    if (marks>60 || marks <=70)
    {
        console.log("BC");
    }
else
    if (marks>50 || marks <=60)
    {
        console.log("CC");
    }
else
    if (marks>40 || marks<=50)
    {
        console.log("CD");
    }
else
    if (marks>30 || marks <=40 )
    {
        console.log("DD");
    }
else
	{
		console.log("FF");
	}