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

var s="FF";
if(marks>90)
    s="AA";
else if(marks>80)
    s="AB";
else if(marks>70)
    s="BB";
else if(marks>60)
    s="BC";
else if(marks>50)
    s="CC";
else if(marks>40)
    s="CD";
else if(marks>30)
    s="DD";

console.log(s);