//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")