//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");