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

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