//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")