//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");