//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 if(marks<=30)
    {
        console.log("FF")
    }