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

if(marks >90)
   console.log("AA");
else if(marks >80 && <= 90)
    console.log("AB");
else if(marks >70 && <= 80)
    console.log("BB");
else if(marks >60 && <= 70)
    console.log("BC");
else if(marks >50 && <= 60)
    console.log("CC");
else if(marks >40 && <= 50)
    console.log("CD");
else if(marks >30 && <= 40)
    console.log("DD");
else if(marks  <= 30)
    console.log("FF");