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

var prnt = "";

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

console.log(prnt);